Ureter, Urinary Bladder, and Kidney





Ureter


Ureteritis Cystica Et Glandularis


Clinical Features





  • One of the most common non-neoplastic urothelial proliferations



  • Reactive urothelial proliferation that develops following an inflammatory stimulus



  • Typically asymptomatic and found incidentally



Gross Pathology





  • Nodular cobblestone appearance due to numerous small, superficial, fluid-filled cysts



Histopathology


Ureteritis Cystica





  • Von Brunn nests (small nests of normal urothelial cells within lamina propria) with central lumens (cystic dilatation) lined by urothelial cells



Ureteritis Glandularis





  • Von Brunn nests with central lumens lined by columnar cells



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Hyperplasia





  • Increase in number of layers of urothelial cells



  • Does not show nesting of urothelial cells



Von Brunn Nests





  • Lacks formation of central cystic dilatation



Pearls





  • Believed by some investigators to be a normal variant of the urothelial mucosa



  • Most believe that an inflammatory stimulus is needed



  • Must be considered in the differential diagnosis of ureteral and renal pelvic filling defects





Selected References




  • Duffin T.K., Regan J.B., Hernandez-Graulau J.M.: Ureteritis cystica with 17-year followup. J Urol 1994; 151: pp. 142-143.



  • Hochberg D.A., Motta J., Brodherson M.S.: Cystitis glandularis. Urology 1998; 51: pp. 112-113.


Urothelial Carcinoma (Transitional Cell Carcinoma)


Clinical Features





  • Relatively rare in the ureter; comprise 2% to 5% of urothelial neoplasms



  • Similar etiologic and pathogenic agents as in bladder urothelial carcinoma: tobacco smoking is the most common risk factor; higher association with analgesic abuse; association with hereditary nonpolyposis colorectal cancer syndrome (HNPCC, Lynch syndrome)



  • Clinical features are comparable to those lesions arising in the urinary bladder and include hematuria and flank pain



  • More commonly results in urinary obstruction



  • Can occur in any portion of the ureter; distal third is most common



Gross Pathology





  • Low-grade tumors typically have a papillary architecture with delicate papillary fronds over the ureteral surface



  • Higher-grade tumors often lack papillary architecture and show nodular, polypoid, or sessile pattern



  • Ureteral wall is typically thickened and may show significant narrowing



  • Ulceration and hemorrhage is often seen in high-grade tumors



Histopathology


Grading of Urothelial Carcinomas





  • To simplify the World Health Organization (WHO) (1973) system and avoid an intermediate cancer grade group (grade II), the WHO (2003)/International Society of Urological Pathology (ISUP) system classifies papillary urothelial carcinomas into only two grades:




    • Low-grade papillary urothelial carcinoma (LG-UC)



    • High-grade papillary urothelial carcinoma (HG-UC)




Low-Grade Papillary Urothelial Carcinoma





  • Exophytic growth pattern characterized by slender papillary fronds with obvious fibrovascular cores, frequent branching, and minimal fusion



  • The papillae are lined by urothelium that shows an orderly appearance with easily recognizable variations in architectural and cytologic features



  • Cells usually show minimal anaplasia; the nuclei are uniformly enlarged with mild differences in shape, contour, and chromatin distribution ( Figure 10.1A )




    Figure 10.1


    A, Low-grade papillary urothelial carcinoma of the ureter. The neoplasm shows a nodular and inverted pattern growth. Cells show minimal anaplasia; the nuclei are uniformly enlarged with mild differences in shape, contour, and chromatin distribution. B, High-grade urothelial carcinoma of the ureter. Ulceration and denudation of the urothelium are often seen in high-grade tumors of the ureter. Cells are large and irregular with moderate to marked nuclear pleomorphism. Infiltration of the underlying subepithelial connective tissue is common.



  • Mitoses are infrequent



High-Grade Papillary Urothelial Carcinoma





  • May lack a distinct papillary architecture, although papillary remnants may persist



  • The papillae are frequently fused and branching



  • The pattern of disorder is predominant with easily recognizable variations in architectural and cytologic features



  • Cells are large and irregular with a spectrum of nuclear pleomorphism ranging from moderate to marked; nucleoli may be prominent ( Figure 10.1B )



  • Bizarre or multinucleated tumor cells may be seen



  • High mitotic activity; numerous atypical forms often seen



  • Usually infiltrates the underlying subepithelial connective tissue or muscularis propria and grows in solid cords or nests



  • Reactive desmoplastic stroma surrounds infiltrating nests of tumor cells



  • Squamous differentiation is seen in more than 20% of cases



Special Stains and Immunohistochemistry





  • Cytokeratin (high molecular weight and CK7), GATA3, and p63: positive



  • Carcinoembryonic antigen (CEA): positive (especially in high-grade tumors); PAX8 positive in a small percentage of cases



Other Techniques for Diagnosis





  • Cytogenetic studies: similar findings as in urothelial carcinoma of the bladder



Differential Diagnosis


Inverted Papilloma





  • Urothelial cords and trabeculae with uniform thickness, peripheral palisading, and central spindling and streaming



  • Minimal cytologic atypia and low mitotic activity



  • Lacks invasion into the muscularis propria



Fibroepithelial Polyp





  • Typically solitary with a short, thin stalk



  • Consists of a polyp of loose fibroconnective and fibrovascular tissue covered by normal-appearing urothelium



Pearls





  • Urine cytology is helpful for evaluating ureteral lesions



  • Prognosis is related to tumor stage (depth of invasion), grade (morphologic and cytologic features), and multifocality (presence of synchronous tumor in the renal pelvis)





Selected References




  • Eble J.N.Sauter G.Epstein J.I. et. al.Pathology and Genetics of Tumours of the Urinary System and Male Genital Organs: World Health Organization Classification of Tumours.2003.IARC PressLyon:



  • Lehmann J., Suttmann H., Kovac I., et. al.: Transitional cell carcinoma of the ureter: prognostic factors influencing progression and survival. Eur Urol 2007; 51: pp. 1281-1288.


Urinary Bladder


Infectious Cystitis





  • Infectious cystitis can be caused by various microorganisms, including bacteria, fungi, viruses, and parasites



  • Diagnosis relies primarily on urinalysis, urine culture, and empirical antimicrobial therapy



Malakoplakia


Clinical Features





  • Inflammatory condition caused by impaired intraphagosomal digestion



  • Most commonly found in the bladder; may be seen in the ureter, renal pelvis, testis, gynecologic tract, gastrointestinal tract, and lung



  • Typically found in women; peak incidence in fifth decade



  • Rarely seen in children



  • Most patients present with typical symptoms of urinary tract infection



  • Often culture Escherichia coli or other bacteria from the urine



Gross Pathology





  • Multiple, soft, yellow-white, nodular plaques measuring less than 2 cm



  • Involves mucosal surface



Histopathology





  • Accumulation of histiocytes with abundant eosinophilic granular cytoplasm (von Hansemann histiocytes) in the superficial lamina propria, typically underlying an intact urothelial layer ( Figure 10.2 )




    Figure 10.2


    Malakoplakia.

    The lamina propria contains numerous histiocytes with a large amount of eosinophilic granular cytoplasm and intracytoplasmic inclusions (Michaelis-Gutmann bodies).



  • Michaelis-Gutmann bodies (small round basophilic intracytoplasmic or extracytoplasmic laminated structures with a bull’s eye appearance) are found within histiocytes as well as within the interstitium



  • Michaelis-Gutmann bodies are formed by precipitation of calcium or iron on bacteria or bacterial fragments



  • Extensive fibrosis or marked acute and chronic inflammation may be seen



Special Stains and Immunohistochemistry





  • Von Kossa calcium and Perl’s Prussian blue: Michaelis-Gutmann bodies are positive



  • Periodic acid-Schiff (PAS): Von Hansemann and Michaelis-Gutmann bodies are positive



Other Techniques for Diagnosis





  • Electron microscopy: Michaelis-Gutmann bodies consist of a dense core surrounded by a homogeneous zone composed of myelin figures; measure 5 to 10 μm in diameter



Differential Diagnosis


Xanthogranulomatous Cystitis





  • Lacks Michaelis-Gutmann bodies



Langerhans Cell Histiocytosis





  • Histiocytes are positive for CD1a and S-100



Pearls





  • Terminology derived from the Greek words plakos (plaque) and malakos (soft)



  • Believed to result from impairment of the ability of mononuclear cells to degrade phagocytosed bacteria



  • Must identify Michaelis-Gutmann bodies in order to make the diagnosis





Selected References




  • Pusl T., Weiss M., Hartmann B., et. al.: Malacoplakia in a renal transplant recipient. Eur J Intern Med 2006; 17: pp. 133-135.



  • Tam V.K., Kung W.H., Li R., Chan K.W.: Renal parenchymal malacoplakia: a rare cause of ARF with a review of recent literature. Am J Kidney Dis 2003; 41: pp. E13-E17.


Noninfectious Cystitis (Polypoid Cystitis, Follicular Cystitis, Giant Cell Cystitis)


Clinical Features





  • Patients may present with urinary frequency, urgency, or dysuria



  • Polypoid cystitis is often seen in patients with indwelling bladder catheters



  • Follicular cystitis is frequently seen in patients with bladder carcinoma and urinary tract infection



  • Giant cell cystitis is not a clinical entity; rather, it is a term used to describe the presence of atypical stromal cells in the lamina propria of the bladder



  • Occasionally seen following radiation treatment



Gross Pathology


Polypoid Cystitis





  • Small polypoid mucosal lesions (may mimic bladder carcinoma)



Follicular Cystitis





  • Mucosa showing erythematous gray-white nodules



Giant Cell Cystitis





  • Usually a subtle finding; erythematous bladder mucosa may be seen



Histopathology


Polypoid Cystitis





  • Broad fronds covered by benign-appearing urothelial cells



  • Lamina propria is edematous with chronic inflammation and congested blood vessels



Follicular Cystitis





  • Lamina propria contains scattered lymphoid follicles, usually with germinal centers



Giant Cell Cystitis





  • Atypical large stromal cells with bipolar or multipolar tapering eosinophilic processes and enlarged hyperchromatic nuclei (degenerative atypia); cells often contain multiple nuclei; mitoses are absent or rare ( Figure 10.3 )




    Figure 10.3


    Giant Cell Cystitis.

    The lamina propria shows atypical large stromal cells with bipolar or multipolar tapering eosinophilic processes and multiple, enlarged hyperchromatic nuclei.



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Bacterial Cystitis





  • Inflammatory component consists of acute inflammatory cells



  • Bladder culture may yield positive results



Low-Grade Papillary Urothelial Carcinoma





  • May be confused with polypoid cystitis



  • Typically shows branching delicate papillae rather than broad fronds



  • Papillae are covered by atypical urothelial cells, which is much more pronounced than that seen in polypoid cystitis



Malignant Lymphoma





  • Must be distinguished from follicular cystitis



  • Lymphomatous infiltrate typically shows a diffuse rather than follicular architecture



Sarcoma





  • Must be distinguished from giant cell cystitis



  • Sarcomatous stromal cells have a higher degree of nuclear atypia; mitoses are commonly found



Pearls





  • Removal of the irritant (catheter, toxin) typically resolves the cystitis



  • Often these conditions are asymptomatic and found incidentally





Selected References




  • Hansson S., Hanson E., Hjalmas K., et. al.: Follicular cystitis in girls with untreated asymptomatic or covert bacteriuria. J Urol 1990; 143: pp. 330-332.



  • Young R.H.: Papillary and polypoid cystitis: a report of eight cases. Am J Surg Pathol 1988; 12: pp. 542-546.


Treatment-Related Cystitis


Clinical Features





  • Bacillus Calmette-Guerin (BCG) cystitis is associated with intravesical instillation of BCG used in the treatment of urothelial carcinoma in situ (CIS) and HG-UC



  • Radiation cystitis may be acute or chronic and can occur whenever the bladder is included in the treatment field



  • Hemorrhagic cystitis is associated with radiation and chemotherapy; also seen with various chemical toxins (cyclophosphamide, busulfan) and viral infection (adenovirus in children), or may be idiopathic



Gross Pathology


Granulomatous Cystitis Secondary to Bacillus Calmette-Guerin Therapy (Bacillus Calmette-Guerin Cystitis)





  • Partially or entirely denuded bladder mucosa



Radiation Cystitis





  • Hyperemic and edematous bladder mucosa with thickened mucosal folds



Hemorrhagic Cystitis





  • Hemorrhagic and edematous bladder mucosa



Histopathology


Bacillus Calmette-Guerin Cystitis





  • Superficial lamina propria shows discrete noncaseating granulomas containing epithelioid histiocytes and multinucleated giant cells



  • Granulomas are associated with intense lymphocytic infiltrate



  • Urothelium may show nonspecific reactive atypia or be denuded



Radiation Cystitis





  • Lamina propria shows edema, hyperemia, and dilated blood vessels with fibrin ( Figure 10.4 )




    Figure 10.4


    A, Radiation cystitis. Lamina propria shows edema, hyperemia, and thickened mucosal folds. The urothelium shows superficial ulceration and atypical cytologic features. The stroma contains extravasated erythrocytes, inflammation, and occasional bizarre multinucleated giant cells. B, Radiation cystitis. Late changes include superficial ulceration and dilated blood vessels with fibrinous exudate.



  • Proliferation of urothelial nests within lamina propria “hugging” ectatic vessels



  • Surface urothelium may shows desquamation, superficial ulceration, and atypical cytologic features mimicking CIS; however, atypia is degenerative and nuclear-cytoplasmic (N:C) ratio is low



  • Bizarre giant cells and multinucleated cells are often present



  • The stroma contains extravasated erythrocytes, inflammation, and hemosiderin deposition



  • Late changes include collagenization of the lamina propria, myointimal proliferation or hyalinization of the arteriole’s media, and often ulceration with fibrinous exudate



Hemorrhagic Cystitis





  • Lamina propria shows hemorrhage and congested blood vessels



  • Urothelium shows regenerative changes including nuclear pleomorphism



  • Healing may result in hyperplastic urothelium with papillae formation



  • Repeated bouts may result in a fibrotic, contracted bladder



Special Stains and Immunohistochemistry





  • Acid-fast stain rarely reveals the presence of microorganisms in BCG cystitis



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Bacterial Cystitis





  • Inflammatory component consists of acute inflammatory cells



  • Bladder culture may yield positive results



Urothelial Carcinoma in Situ





  • Cytologic atypia and architectural distortion are more pronounced and mitoses are frequently found



Pearls





  • Acute symptoms of radiation cystitis may appear 4 to 6 weeks after the initiation of treatment; late symptoms appear as late as 10 years later



  • Pathologist must be aware that these changes may be seen with a remote radiation or chemotherapy history



  • Accurate clinical history is key to avoid misdiagnosis





Selected References




  • Chan T.Y., Epstein J.I.: Radiation or chemotherapy cystitis with “pseudocarcinomatous” features. Am J Surg Pathol 2004; 28: pp. 909-913.



  • Wong-You-Cheong J.J., Woodward P.J., Manning M.A., et. al.: From the archives of the AFIP: inflammatory and nonneoplastic bladder masses: radiologic-pathologic correlation. Radiographics 2006; 26: pp. 1847-1868.


Interstitial (Hunner) Cystitis


Clinical Features





  • Classically occurs in middle-aged and elderly women



  • Interstitial cystitis is manifested by sensory hypersensitivity; patients present with urinary frequency, urgency, nocturia, suprapubic pressure, and pelvic and bladder pain



  • Hematuria may be seen



  • Urine is sterile and thus bladder culture is negative



Gross Pathology





  • Cystoscopy may show petechial hemorrhage after inflation (glomerulation) and small linear ulcerations in the mucosa (Hunner ulcer)



  • Scarring of bladder mucosa is often noted



  • Longstanding cases may result in a fibrotic, contracted bladder with markedly diminished capacity



  • Usually affects dome and posterolateral bladder walls



Histopathology


Nonulcerative or Early Disease





  • Multiple microhemorrhages are present within the lamina propria (glomerulations)



  • Classic phase (Hunner ulcer)



  • Single or multiple patches of reddened, ulcerated, or denuded bladder mucosa with fibrinous exudate often seen admixed with chronic inflammatory cells, including lymphocytes, plasma cells, and mast cells



  • Characteristic feature is increase in mast cells within the mucosa, lamina propria, and muscularis propria



  • Hemorrhage, edema, congestion, and fibrosis are also seen



  • Occasionally there is no ulceration of the mucosa; only chronic inflammation, edema, hemorrhage, and granulation tissue are seen



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Flat Urothelial Carcinoma in Situ





  • Denuding CIS exhibits ulceration, vascular congestion, and inflammation resembling interstitial cystitis



  • Multiple tissue sections should be examined to search for atypical cells



Bacterial Cystitis





  • Inflammatory component consists of acute inflammatory cells



  • No increase in mast cells



  • Bladder culture may yield positive results



Noninfectious Cystitis





  • Features of polypoid cystitis, follicular cystitis, giant cell cystitis, or hemorrhagic cystitis



  • No increase in mast cells



Pearls





  • Only nonspecific features exist and must be correlated with clinical impression; no pathognomonic microscopic features currently exist



  • Exclude CIS before a diagnosis of interstitial cystitis is rendered





Selected References




  • Chai T.C., Keay S.: New theories in interstitial cystitis. Nat Clin Pract Urol 2004; 1: pp. 85-89.



  • Mayer R.: Interstitial cystitis pathogenesis and treatment. Curr Opin Infect Dis 2007; 20: pp. 77-82.



  • Sant G.R., Kempuraj D., Marchand J.E., et. al.: The mast cell in interstitial cystitis: role in pathophysiology and pathogenesis. Urology 2007; 69: pp. 34-40.


Cystitis Cystica Et Glandularis


Clinical Features





  • Common non-neoplastic lesion of the bladder



  • Believed to be induced by chronic inflammatory stimulus



  • Found most commonly in adults; occasionally seen in children



  • Cystoscopically may occasionally mimic carcinoma



Gross Pathology


Cystitis Cystica





  • Small submucosal cysts filled with clear yellow fluid



Cystitis Glandularis





  • May not always be grossly visible



  • Occasionally see irregular nodular mucosa



Histopathology


Cystitis Cystica





  • Von Brunn nests within the lamina propria showing central cystic dilatation with spaces lined by urothelial or low cuboidal epithelium ( Figure 10.5 )




    Figure 10.5


    Cystitis Cystica et Glandularis.

    The lamina propria shows cystically dilated glands lined by urothelial cells (right). In some cases the epithelial lining undergoes glandular metaplasia with intestinal-type goblet cells (left). This variant is called cystitis glandularis with intestinal metaplasia.



  • Cysts are often filled with pale eosinophilic fluid



Cystitis Glandularis





  • The epithelial lining of von Brunn nests undergoes glandular metaplasia



  • Glands are lined by cuboidal to columnar cells without anaplasia



  • Cells may contain mucin and occasionally goblet cells are present



  • If the epithelium acquires intestinal-type goblet cells, this variant is called cystitis glandularis with intestinal metaplasia (if diffuse without urothelial cells: colonic metaplasia)



Special Stains and Immunohistochemistry





  • Reactive urothelium shows CK20 immunoreactivity in only the umbrella cell layer



  • p53 nuclear staining is predominantly negative with occasional weak positivity in the basal and parabasal intermediate cells



  • CD44 can be overexpressed in the entire reactive urothelium or focally positive in intermediate cells



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Carcinoma, Nested Variant





  • Florid von Brunn nest can be differentiated from nested variant of urothelial carcinoma by its lobular or linear array of the nests, flat noninfiltrative base, and lack of cytologic atypia



Adenocarcinoma





  • Rare bladder neoplasm



  • Atypical glands lined by stratified, pleomorphic cells with infiltration into the muscular layer



  • Signet ring cells may be seen



Pearls





  • Florid von Brunn nests, cystitis cystica, and cystitis glandularis are closely related reactive changes that may be seen in any portion of the urothelial tract



  • Cystitis cystica et glandularis has no direct association with bladder cancer; coincidental coexistence may be seen



  • Cystitis glandularis may be confused with adenocarcinoma, especially if extravasated mucin is present



  • Believed to be associated with chronically irritated bladders; may resolve if source of inflammation is removed





Selected References




  • McKenney J.K., Desai S., Cohen C., Amin M.B.: Discriminatory immunohistochemical staining of urothelial carcinoma in situ and non-neoplastic urothelium: an analysis of cytokeratin 20, p53, and CD44 antigens. Am J Surg Pathol 2001; 25: pp. 1074-1078.



  • Tamas E.F., Epstein J.I.: Detection of residual tumor cells in bladder biopsy specimens: pitfalls in the interpretation of cytokeratin stains. Am J Surg Pathol 2007; 31: pp. 390-397.



  • Volmar K.E., Chan T.Y., De Marzo A.M., Epstein J.I.: Florid von Brunn nests mimicking urothelial carcinoma: a morphologic and immunohistochemical comparison to the nested variant of urothelial carcinoma. Am J Surg Pathol 2003; 27: pp. 1243-1252.



  • Young R.H., Bostwick D.G.: Florid cystitis glandularis of intestinal type with mucin extravasation: a mimic of adenocarcinoma. Am J Surg Pathol 1996; 20: pp. 1462-1468.


Nephrogenic Adenoma


Clinical Features





  • Most cases involve the bladder; occasionally found in the urethra, ureter, or renal pelvis



  • Found in young adults with a male predominance (2:1)



  • Approximately half of the cases are found following genitourinary surgery, including renal transplantation



  • Also associated with calculi, trauma, and cystitis



  • Often asymptomatic, although patients frequently present with hematuria or dysuria



Gross Pathology





  • Usually found over the posterior bladder wall



  • May present as a papillary or polypoid exophytic mass or velvety lesion



  • Sessile forms comprise approximately 25% to 30% of cases



  • Papillary structures usually measure less than 1 cm; may rarely measure greater than 5 cm



Histopathology





  • Classic histologic pattern is that of small tubules resembling renal tubules ( Figure 10.6A )




    Figure 10.6


    A, Nephrogenic adenoma. Proliferation of small tubules lined by cuboidal epithelium. No mitotic activity or nuclear pleomorphism are noted. Tubules are often surrounded by a layer of hyalinized basement membrane. Pale eosinophilic secretions are often found within the tubules. B, Nephrogenic adenoma. Papillary fronds lined by cuboidal eosinophilic cells with occasional “hobnail” features.



  • May also see papillary or flat architecture



  • Tubules are lined by “hobnail” cells resembling endothelial-lined vascular spaces ( Figure 10.6B )



  • Tubules are often surrounded by a layer of hyalinized basement membrane



  • Cells with oxyphilic or clear cytoplasm, or signet-ring–like cells, may also be seen



  • Mitotic activity is rare



  • Pale eosinophilic secretions are often found within the tubules



  • A variable degree of acute and chronic inflammation and stromal edema are common in the background



  • Typically confined to the lamina propria, it can on occasion focally involve the superficial lamina propria; rarely may have a deep infiltrative pattern into perinephric adipose tissue



Special Stains and Immunohistochemistry





  • Cytokeratin 7 (CK7), PAX2, and PAX8 are positive in the tubular lining cells



  • Focal and weak prostate-specific antigen (PSA) and PAP expression is detected in a subset of cases



  • Most cases are positive for AMACR and negative for high molecular weight cytokeratin (34BE12)



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Prostatic and Clear Cell Adenocarcinoma





  • Not typically associated with other clinical conditions



  • Tubules with prominent nucleoli sometimes situated within muscle bundles



  • Usually much larger



  • Shows greater cytologic atypia and high mitotic rate



Low-Grade Papillary Urothelial Carcinoma





  • Papillae are covered by neoplastic urothelial cells rather than benign-appearing cuboidal cells



  • Nested or microcystic variant of urothelial carcinoma exhibits greater atypia and increased mitoses at the deep invasive fronts



Capillary Hemangioma





  • Negative for CK7 and positive for endothelial markers, such as CD31



Pearls





  • Evidence in renal transplant patients suggests that nephrogenic adenoma is derived from tubular renal cells and is not a metaplastic proliferation of the urothelium





Selected References




  • Diolombi M., Ross H.M., Mercalli F., et. al.: Nephrogenic adenoma: a report of 3 unusual cases infiltrating into perinephric adipose tissue. Am J Surg Pathol 2013; 37: pp. 532-538.



  • Piña-Oviedo S., Shen S.S., Truong L.D., et. al.: Flat pattern of nephrogenic adenoma: previously unrecognized pattern unveiled using PAX2 and PAX8 immunohistochemistry. Mod Pathol 2013; 26: pp. 792-798.


Flat Urothelial Lesions


In 1998, the WHO/ISUP published a consensus classification. The following entities were included in the category for flat urinary bladder lesions: flat urothelial hyperplasia and flat lesion with atypia, which is further divided into reactive atypia, atypia of unknown significance, urothelial dysplasia (low-grade intraepithelial neoplasia), and flat urothelial CIS (high-grade intraepithelial neoplasia). Because the 2003 WHO has accepted the nomenclature used in 1998, the system is currently referred to as WHO (2003)/ISUP.


Urothelial Hyperplasia


Clinical Features





  • Rare benign urothelial lesion; it may be seen in the flat mucosa adjacent to a low-grade papillary urothelial lesion



Gross Pathology





  • Noncontributory



Histopathology





  • Markedly thickened urothelial mucosa without cytologic atypia



  • Rather than requiring a specific number of cell layers, marked thickening compared with the adjacent normal urothelium is needed to diagnosis flat hyperplasia



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Frequent deletions of chromosome 9 detected by fluorescence in situ hybridization (FISH) have been reported in urothelial hyperplasias found in patients with papillary bladder cancer



Differential Diagnosis


Urothelial Dysplasia





  • Variable, often appreciable, loss of cell polarity with nuclear crowding and cytologic atypia that is not severe enough to merit a diagnosis of CIS



Urothelial Carcinoma in Situ





  • Pleomorphism, prominent nucleoli throughout the urothelium and upper-level mitoses



Pearls





  • Regarded in the new WHO classification as a lesion without malignant potential



  • Molecular analysis has shown that urothelial hyperplasia in bladder cancer patients may be chronologically related to papillary tumors



  • In the absence of an associated papillary urothelial neoplasm, no treatment or follow-up is required





Selected References




  • Hartmann A., Moser K., Kriegmair M., et. al.: Frequent genetic alterations in simple urothelial hyperplasias of the bladder in patients with papillary urothelial carcinoma. Am J Pathol 1999; 154: pp. 721-727.



  • van Oers J.M., Adam C., Denzinger S., et. al.: Chromosome 9 deletions are more frequent than FGFR3 mutations in flat urothelial hyperplasias of the bladder. Int J Cancer 2006; 119: pp. 1212-1215.


Urothelial Dysplasia


Clinical Features





  • De novo dysplasia affects predominantly middle-aged men presenting occasionally with irritative bladder symptoms with or without hematuria



Gross Pathology





  • Lesion may be inapparent or associated with erythema, erosion, or (rarely) ulceration



Histopathology





  • Shows variable, often appreciable, loss of cell polarity, with nuclear crowding and cytologic atypia, that is not severe enough to merit a diagnosis of CIS ( Figure 10.7 )




    Figure 10.7


    Urothelial Dysplasia.

    The urothelium shows nuclear crowding and cytologic atypia. The cells have mildly altered chromatin distribution, slightly enlarged nuclei, inconspicuous nucleoli, and rare mitoses.



  • Cells may have mildly altered chromatin distribution, slightly enlarged nuclei, inconspicuous nucleoli, and rare mitoses



  • The thickness of the urothelium is usually normal; however, it may be increased or decreased



  • Lamina propria may contain increased inflammation or neovascularity



  • Urothelial dysplasia may involve von Brunn nests



Special Stains and Immunohistochemistry





  • Aberrant CK20 expression



  • p53 and Ki-67 overexpression



Other Techniques for Diagnosis





  • Alteration of chromosome 9 and p53 allelic losses have been demonstrated



Differential Diagnosis


Urothelial Carcinoma in Situ





  • Typically shows pleomorphism, and prominent nucleoli throughout the urothelium



  • Increased mitotic activity with upper-level mitosis



  • Coarse chromatin pattern



Reactive Inflammatory Atypia





  • Presence of acute and chronic inflammation



Urothelial Atypia of Unknown Significance





  • Presence of significant atypia and significant inflammation



Pearls





  • Dysplasia in patients with noninvasive papillary neoplasms indicates urothelial instability and a marker for progression or recurrence



  • De novo dysplasia progresses to urothelial neoplasia in 5% to 19% of patients




Selected References


Amin MB, McKenney JK. An approach to the diagnosis of flat intraepithelial lesions of the urinary bladder using the World Health Organization/International Society of Urological Pathology consensus classification system. Adv Anat Pathol. 2002;9:222–232.


Hodges KB, Lopez-Beltran A, Davidson DD, et al. Urothelial dysplasia and other flat lesions of the urinary bladder: clinicopathologic and molecular features. Hum Pathol. 2010;41:155–162.


Urothelial Carcinoma in Situ


Clinical Features





  • Patients are usually in their fifth to sixth decade



  • Asymptomatic or symptomatic with dysuria, frequency, urgency, or even hematuria



  • CIS is commonly multifocal and may be diffuse



  • De novo (primary) CIS accounts for less than 1% to 3% of urothelial neoplasms but is seen in association with 45% to 65% of invasive urothelial carcinomas



Gross Pathology





  • Bladder mucosa may be unremarkable or erythematous and edematous



Histopathology





  • Urothelial CIS is a nonpapillary (i.e., flat) lesion in which the surface epithelium contains cytologically malignant cells ( Figure 10.8 )




    Figure 10.8


    Urothelial Carcinoma In Situ.

    The entire thickness of the urinary bladder epithelium is replaced by neoplastic cells. There is complete loss of polarity, marked crowding, and pleomorphism. Nuclei are hyperchromatic and have a coarse or condensed chromatin distribution.



  • The term CIS is synonymous with “high-grade intraurothelial neoplasia”



  • Nuclear anaplasia identical to HG-UC



  • The urothelium may be denuded, diminished in thickness, of normal thickness, or even hyperplastic



  • There may be complete loss of polarity, marked crowding, and pleomorphism



  • Nuclei are frequently hyperchromatic and have a coarse or condensed chromatin distribution



Special Stains and Immunohistochemistry





  • CK20: diffuse strong cytoplasmic staining involving the full thickness of urothelium



  • p53: nuclear staining may be diffuse throughout the full thickness



  • CD44: expression limited to residual basal cell layer or negative



Other Techniques for Diagnosis





  • Chromosome 9 deletions and p53 allelic losses have been frequently demonstrated



Differential Diagnosis


Urothelial Dysplasia





  • Cytologic atypia is not severe enough to merit a diagnosis of CIS



  • Lacks pleomorphism comparable to high-grade papillary carcinoma, discohesion, or mitoses in the upper urothelium



Reactive Atypia





  • Lacks nuclear pleomorphism



  • Presence of acute and chronic inflammation



Urothelial Atypia of Unknown Significance





  • Presence of significant atypia and significant inflammation



Radiation-Induced Atypia





  • Florid epithelial proliferation with cell enlargement, hyperchromasia, and prominent nucleoli



  • Stromal fibrosis, subepithelial hemorrhage, and hyalinization of blood vessels



Polyoma Virus Infection





  • Nucleomegaly, high N:C ratio, and hyperchromasia



  • Homogeneous, smudgy, basophilic, opaque nuclear inclusion



  • Smooth nuclear membranes; nucleoli are absent



Pearls





  • De novo CIS is less likely to progress to invasive disease than is secondary CIS



  • BCG immunotherapy remains the most effective treatment and prophylaxis for CIS, reducing short-term tumor recurrence by about 20% and long-term recurrence by about 7%; however disease progression, and mortality are not significantly reduced




Selected References


Oliva E, Pinheiro NF, Heney NM, et al. Immunohistochemistry as an adjunct in the differential diagnosis of radiation-induced atypia versus urothelial carcinoma in situ of the bladder: a study of 45 cases. Hum Pathol . 2013;44:860–866.


Yin H, He Q, Li T, Leong AS. Cytokeratin 20 and Ki-67 to distinguish carcinoma in situ from flat non-neoplastic urothelium. Appl Immunohistochem Mol Morphol . 2006;14:260–265.


Papillary Urothelial Lesions


The WHO (2003)/ISUP classification of noninvasive papillary urothelial lesions comprises papillary hyperplasia, urothelial papilloma and inverted papilloma, papillary neoplasm of low malignant potential, and low-grade (LG) and HG-UC. To avoid an intermediate cancer grade group (grade II), the WHO (2003)/ISUP system classifies papillary urothelial carcinoma into only two grades: LG-UC and HG-UC.


Papillary Urothelial Hyperplasia


Clinical Features





  • Typically discovered on routine follow-up cystoscopy for papillary urothelial neoplasms



Gross Features





  • Benign focally elevated lesion identified at cystoscopy, described as papillary, raised, sessile, or bleblike



Histopathology





  • Undulating urothelium arranged into mucosal narrow papillary folds of varying heights; no detached papillary fronds



  • The urothelium within papillary hyperplasia and the adjacent flat mucosa are often thicker than normal



  • The cytologic findings are similar to those characteristic of normal urothelium



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Papilloma





  • Well-developed, detached papillary fronds with branching fibrovascular cores of a papillary neoplasm are evident



Pearls





  • Patients should be followed, as papillary hyperplasia likely represents the precursor lesion to low-grade papillary urothelial neoplasms





Selected References




  • Swierczynski S.L., Epstein J.I.: Prognostic significance of atypical papillary urothelial hyperplasia. Hum Pathol 2002; 33: pp. 512-517.



  • Taylor DC, Bhagavan BS, Larsen MP, et al. Papillary urothelial hyperplasia: a precursor to papillary neoplasms. Am J Surg Pathol. 1996; 20:1481–1488.


Urothelial Papilloma


Clinical Features





  • Benign papillary urothelial tumor lined by normal-appearing urothelium



  • Slightly more common in men



  • Tends to occur in younger patients and is seen in children



  • Usually presents with gross hematuria



Gross Features





  • Urothelial papillomas typically have a simple papillary architecture



Histopathology





  • Papillary fronds are lined by normal-appearing urothelium, lacking atypia ( Figure 10.9 )




    Figure 10.9


    Urothelial Papilloma.

    Papillary fronds are lined by normal-appearing urothelium. Superficial umbrella cells are often prominent, with abundant eosinophilic cytoplasm and vacuolization.



  • Usually have a simple minimally branching arrangement and slender fibrovascular stalks with a predominantly exophytic pattern



  • Superficial umbrella cells are often prominent, with abundant eosinophilic cytoplasm, and vacuolization



  • Mitoses are absent



Special Stains and Immunohistochemistry





  • Cytokeratin 20: confined to the umbrella cells, similarly to normal urothelium



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Papillary Neoplasm of Low Malignant Potential (PUNLMP)





  • Markedly thickened urothelium



  • Mitoses may be present but are confined to the basal layers



Pearls





  • Rarely recur; can progress to higher-grade disease



  • Complete transurethral resection is the treatment of choice




Selected References


Magi-Galluzzi C, Epstein JI. Urothelial papilloma of the bladder: a review of 34 de novo cases. Am J Surg Pathol . 2004;28:1615–1620.


McKenney JK, Amin MB, Young RH. Urothelial (transitional cell) papilloma of the urinary bladder: a clinicopathologic study of 26 cases. Mod Pathol . 2003;16:623–629.


Inverted Papilloma


Clinical Features





  • Rare benign urothelial tumor of unknown etiology



  • More common in males and occurs at all ages; median age is 55 years



  • Typically involves the bladder at the trigone, bladder neck, or prostatic urethra



  • Frequently presents with hematuria



Gross Pathology





  • Typically solitary flat or slightly raised polypoid mass with smooth contours



  • Usually minimal exophytic component



  • Most are smaller than 3 cm in diameter



Histopathology





  • Characterized by anastomosing cords or islands of urothelium showing uniform width and minimal cytologic atypia; rare mitotic activity ( Figure 10.10A )




    Figure 10.10


    A, Inverted papilloma. The urothelial cells show minimal cytologic atypia. B, Inverted papilloma. Tumor originates from the surface urothelium and extends down into the underlying lamina propria. It forms anastomosing cords or islands of urothelium.



  • Tumor originates from the surface urothelium and extends down into the underlying lamina propria but not into the muscular bladder wall ( Figure 10.10B )



  • Small cystic spaces and true glandular differentiation with layer of mucin secreting cells may be seen



  • The stromal component is mostly minimal and lacks inflammation



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Carcinoma





  • Typically shows an exophytic papillary architecture



  • Increased cytologic atypia and increased mitotic activity



  • Invasive growth pattern is often noted



Florid Proliferation of von Brunn Nests





  • Round nests without the anastomosing pattern



Pearls





  • Relationship between inverted papilloma and low-grade papillary urothelial carcinoma is not fully understood



  • Inverted papilloma is best treated by transurethral resection; occasional recurrences have been reported



  • Occasionally coexistence with papillary urothelial carcinoma has been described, although it is unresolved whether there is an increased risk of this relationship




Selected References


Patel P, Reikie BA, Maxwell JP, et al. Long-term clinical outcome of inverted urothelial papilloma including cases with focal papillary pattern: is continuous surveillance necessary? Urology . 2013;82:857–860.


Sung MT, MacLennan GT, Lopez-Beltran A, et al. Natural history of urothelial inverted papilloma. Cancer . 2006;107:2622–2627.


Papillary Urothelial Neoplasm of Low Malignant Potential


Clinical Features





  • Papillary urothelial neoplasm lined by urothelium with minimal atypia



  • Slightly more common in men



  • Mean age at diagnosis is 64.6 years (ranges from 29 to 94 years)



  • Usually presents with gross or microscopic hematuria



Gross Features





  • Small to 2-cm papillary tumor



Histopathology





  • Discrete and slender papillary fronds lined by a thickened multilayered urothelium with minimal to absent cytologic atypia ( Figure 10.11 )




    Figure 10.11


    Papillary urothelial neoplasm of low malignant potential.

    Discrete and slender papillary frond lined by a thickened multilayered urothelium with minimal to absent cytologic atypia.



  • Cell density appears to be increased compared to normal



  • Polarity is preserved



  • Mitoses are rare and have a basal location



Special Stains and Immunohistochemistry





  • Cytokeratin 20: confined to the umbrella cells



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Noninvasive Low-Grade Papillary Urothelial Carcinoma





  • Scattered cells with enlarged hyperchromatic nuclei



  • More than rare mitotic figures



Urothelial Papilloma





  • Lining urothelium is of normal thickness



Pearls





  • Recurrences occur but at a lower frequency than with papillary carcinoma



  • Transurethral resection is the treatment of choice




Selected References


Jones TD, Cheng L. Papillary urothelial neoplasm of low malignant potential: evolving terminology and concepts. J Urol . 2006; 175:1995–2003.


Lee TK, Chaux A, Karram S, et al. Papillary urothelial neoplasm of low malignant potential of the urinary bladder: clinicopathologic and outcome analysis from a single academic center. Hum Pathol . 2011; 42:1799–1803.


Noninvasive Low-Grade Papillary Urothelial Carcinoma


Clinical Features





  • Papillary neoplasm lined by urothelium with easily recognizable variation in architectural and cytologic features



  • Slightly more common in men



  • Mean age at diagnosis is 69.2 years (ranges from 28 to 90 years)



  • Usually presents with gross or microscopic hematuria



Gross Features





  • In the majority of the cases, the papillary tumor is single



Histopathology





  • Slender papillary fronds showing frequent branching and minimal fusion ( Figure 10.12 )




    Figure 10.12


    Noninvasive low-grade papillary urothelial carcinoma.

    Slender papillary frond lined by an orderly urothelium with easily recognizable variations in architectural and cytologic features. The nuclei are uniformly enlarged with mild differences in shape, contour, and chromatin distribution.



  • Lesion shows an orderly appearance with easily recognizable variations in architectural and cytologic features



  • Nuclei are uniformly enlarged with mild variation in shape, contour, and chromatin distribution



  • Mitoses are infrequent and may occur at any level



Special Stains and Immunohistochemistry





  • p53 and Ki-67 expression is intermediate between papillary urothelial neoplasm of low malignant potential and high-grade urothelial carcinoma



  • Negative or focal reactivity for CK20



Other Techniques for Diagnosis





  • Allelic loss of multiple chromosome loci has been reported



Differential Diagnosis


Papillary Urothelial Neoplasm of Low Malignant Potential





  • Monotonous bland-appearing cells, lacking scattered cells with enlarged hyperchromatic nuclei



High-grade Papillary Urothelial Carcinoma





  • High degree of cytologic atypia with architectural distortion



Pearls





  • Recurrence is common in approximately 48% to 71% of patients



  • Progression to invasion and cancer deaths occurs in less than 5% of patients



  • Transurethral resection is the treatment of choice; multifocal or recurrent disease is sometimes treated with intravesical immunotherapy




Selected References


Vardar E, Gunlusoy B, Minareci S, et al. Evaluation of p53 nuclear accumulation in low- and high-grade (WHO/ISUP classification) transitional papillary carcinomas of the bladder for tumor recurrence and progression. Urol Int . 2006;77:27–33.


Wu XR. Urothelial tumorigenesis: a tale of divergent pathways. Nat Rev Cancer . 2005;5:713–772.


Noninvasive High-Grade Papillary Urothelial Carcinoma


Clinical Features





  • Usually presents with gross or microscopic hematuria



Gross Features





  • Appearance varies from papillary to nodular/solid sessile lesion



Histopathology





  • Papillary neoplasm characterized by a disorderly appearance of urothelium resulting from marked architectural and cytologic abnormalities, recognizable at low magnification



  • Papillae are frequently fused and branching, although some may be delicate; extensive denudation may be present ( Figure 10.13 )




    Figure 10.13


    Noninvasive high-grade papillary urothelial carcinoma.

    Papillae are frequently fused and branching. Cytologically, there is moderate to marked pleomorphism with marked variation in nuclear polarity, size, shape, and chromatin pattern.



  • Cytologically, there is a spectrum of pleomorphism ranging from moderate to marked



  • There is marked variation in nuclear polarity, size, shape, and chromatin pattern; nucleoli may be prominent



  • Mitotic figures, including atypical forms, are frequently seen at all levels of the urothelium



Special Stains and Immunohistochemistry





  • Detection of p53 and ki67 is more frequent than in low-grade urothelial carcinoma



  • Strong and diffuse reactivity for p16 and CK20



Other Techniques for Diagnosis





  • Deletion of chromosome 9p seems to be an early event in the development of papillary urothelial carcinoma



Differential Diagnosis


Low-Grade Papillary Urothelial Carcinoma





  • Mild degree of cytologic atypia with minimum architectural distortion



Pearls





  • Urothelial carcinoma with both low- and high-grade features is not uncommon



  • Invasion both within the papillary cores and at the base of the lesions should be ruled out




Selected References


Chaux A, Karram S, Miller JS, et al. High-grade papillary urothelial carcinoma of the urinary tract: a clinicopathologic analysis of a post-World Health Organization/International Society of Urological Pathology classification cohort from a single academic center. Hum Pathol . 2012;43:115–120.


Mai KT, Flood TA, Williams P, et al. Mixed low- and high-grade papillary urothelial carcinoma: histopathogenetic and clinical significance. Virchows Arch . 2013;463:575–581.


Owens CL, Epstein JI. Significance of denuded urothelium in papillary urothelial lesions. Am J Surg Pathol . 2007;31:298–303.


Invasive Urothelial Carcinoma


Clinical Features





  • Typically found in elderly individuals with a mean age older than 65 years



  • More frequently seen in men M:F = 3:1



  • Associated with tobacco smoking, many toxic chemicals (including nitrosamines), drugs (phenacetin, cyclophosphamide), infections ( Schistosoma hematobium )



  • Most common presenting symptom is painless hematuria



  • Patients may have flank pain and obstructive symptoms



Gross Features





  • Tumors usually involve the lateral or posterior bladder walls; occasionally involve the bladder dome



  • Low-grade tumors typically have a papillary architecture appearing as multiple finger-like fronds over the bladder mucosa (see Noninvasive LG-UC)



  • Higher-grade tumors often lack papillary architecture and show nodular, polypoid, or sessile pattern (see Noninvasive HG-UC); focal remnants of papillary architecture may persist



  • Bladder wall is typically thickened, firm, and gray-white



  • Ulceration and hemorrhage are often seen in the high-grade tumors



Histopathology


Urothelial Carcinoma Invading Lamina Propria (PT1)





  • Foci of invasion are characterized by urothelial nests, clusters, or single cells within the papillary cores or lamina propria ( Figure 10.14 )




    Figure 10.14


    High-grade urothelial carcinoma invading lamina propria.

    Foci of invasion are characterized by urothelial nests within the lamina propria.



  • Reactive desmoplastic stroma surround infiltrating nests of tumor cells



  • Foci of invasive tumor may be associated with retraction artifact, mimicking vascular invasion



Urothelial Carcinoma Invading Muscularis Propria (PT2)





  • Usually nonpapillary tumors infiltrate the underlying muscularis propria



  • Muscularis propria invasion is diagnosed when carcinoma infiltrates between thick distinct fascicles of muscle bundles



  • Muscle invasion may or may not elicit a desmoplastic stromal response



  • Even in cases of noninvasive disease, the pathologist should note whether muscularis propria is present in the biopsy specimen



Urothelial Carcinoma Invading Adipose Tissue and Surrounding Organs (PT3 and PT4)





  • Adipose tissue is often present between detrusor muscle bundles, thus the presence of tumor in fat in a biopsy does not necessarily equate with involvement of perivesical fat



Invasive Urothelial Carcinoma: Histologic Variants





  • Urothelial carcinoma has a propensity for divergent differentiation with the most common being squamous followed by glandular



  • Presence of variant histology in general has no impact on clinical outcomes, although such tumors often have other adverse pathologic features such as higher stage



Infiltrating Urothelial Carcinoma With Squamous Differentiation





  • Occurs in 21% of urothelial carcinomas of the bladder and 44% of tumors of the renal pelvis



  • Clinical significance of squamous differentiation remains uncertain



Infiltrating Urothelial Carcinoma With Glandular Differentiation





  • Tubular or enteric glands with mucin secretions may be present in about 6% of urothelial carcinoma of the bladder



Infiltrating Urothelial Carcinoma, Nested Variant





  • Aggressive neoplasm, with 70% of the patients dead 4 to 40 months after diagnosis, despite therapy



  • This variant has a deceptively benign appearance that closely resembles von Brunn nests infiltrating the lamina propria ( Figure 10.15 )




    Figure 10.15


    Infiltrating urothelial carcinoma, nested variant.

    This variant of urothelial carcinoma is characterized by closely packed, irregularly invading, crowded, or anastomosing nests of relatively bland neoplastic cells infiltrating the lamina propria.



Infiltrating Urothelial Carcinoma, Large Nested Variant





  • Contains unevenly distributed medium to large cell nests with rounded to irregular contours, typically separated by abundant fibrous stromal tissue ( Figure 10.16 )




    Figure 10.16


    Infiltrating urothelial carcinoma, large nested variant.

    Tumor shows unevenly distributed large cell nests with rounded to irregular contours, separated by abundant fibrous stromal tissue.



  • Displays deceptively bland cytologic features, often mimicking low-grade urothelial carcinoma



  • Tumors frequently have a surface component, often of LG-UC, although in rare cases there may be an associated high-grade papillary component



  • Invasion into the muscularis propria is commonly present with occasional cases displaying invasion into perivesical tissue



Infiltrating Urothelial Carcinoma, Micropapillary Variant





  • Resembles papillary serous carcinoma of the ovary



  • Surface of the tumors shows slender, delicate papillary and villiform processes, often without a central vascular core



  • Invasive portion is characterized by minute nests of cells or fine papillae contained within tissue retraction spaces, simulating lymphatic spaces



  • Tumors are invariably muscle invasive, high grade



Infiltrating Urothelial Carcinoma, Lymphoepithelioma-Like





  • Morphology is similar to lymphoepithelioma-like carcinoma in other organs with nests of tumor cells heavily infiltrated and masqueraded by lymphoplasmacytic cells



  • Proportion of lymphoepithelioma-like carcinoma should be reported



  • Behavior is uncertain as only few cases have been reported



  • Pure form of lymphoepithelioma-like carcinoma is responsive to chemotherapy



Grading of Urothelial Carcinoma (See Noninvasive Low- and High-Grade Papillary Urothelial Carcinomas)


Special Stains and Immunohistochemistry





  • Cytokeratin (high molecular weight, CK7, CK20), p63, and CD15: positive



  • CEA: positive (especially in high-grade tumors)



  • GATA3: positive



Other Techniques for Diagnosis





  • Cytogenetic studies: deletion of chromosome 9p is associated with superficial disease; abnormalities involving chromosome 17p are associated with disease progression; aneuploidy involving chromosomes 3, 7, and 17



Differential Diagnosis


Polypoid Cystitis





  • Must be distinguished from low-grade papillary transitional cell carcinoma



  • Usually shows wider papillary structures and stromal edema



  • Urothelium may show reactive atypia but usually less dysplasia than in transitional cell carcinoma



Florid von Brunn Nests





  • Must be distinguished from nested and large nested variants of urothelial carcinoma



  • Lobulated architecture with flat, noninvasive base



  • Urothelial nests of relatively uniform size and shape and often associated with cystitis cystica et glandularis



  • No significant cytologic atypia



Nephrogenic Adenoma





  • Must be distinguished from glandular component of urothelial carcinoma with glandular differentiation



  • Classic histologic pattern is that of small tubules resembling renal tubules



  • Papillary architecture can be confused with urothelial carcinoma



  • Papillae and tubules are lined by benign cuboidal cells



  • PAX2 and PAX8 positive, P63 and GATA3 negative



Inverted Papilloma





  • Minimal cytologic atypia and low mitotic activity



  • Lacks invasion into the muscularis propria



Low-Grade Papillary Urothelial Carcinoma With Inverted Growth Pattern





  • Must be distinguished from large nested variant of urothelial carcinoma



  • Lacks invasive appearance and invasion into the muscularis propria



  • Has rounded nests, which are fairly uniform in size and usually crowded



Squamous Cell Carcinoma





  • Pure squamous lesions lacking in situ and invasive urothelial component



  • If an urothelial component is seen, the lesion should be classified as urothelial carcinoma with squamous differentiation



Lymphoma





  • Must distinguish from lymphoepithelioma-like variant of urothelial carcinoma



  • Islands of high-grade epithelial cells are not seen



  • Cytokeratin is negative



  • Leukocyte common antigen (LCA) is diffusely positive



Prostatic Adenocarcinoma





  • Must distinguish from poorly differentiated bladder cancer



  • Specimen is often obtained from the trigone or bladder neck



  • p63, GATA3, and thrombomodulin are negative



  • PSA, prostate-specific acid phosphatase (PSAP), prostate specific membrane antigen (PSMA), p501s (prostein), and NKX3.1 are positive



Pearls





  • Urine cytology is a valuable tool for managing patients with bladder cancer, especially high grade (best used as monitor for therapeutic response)



  • Superficial urothelial tumors include those tumors that are confined to the lamina propria (stage T1); invasive cancer includes lesions that have invaded into the superficial muscularis propria (detrusor muscle) (stage T2a), deep muscularis propria (stage T2b), perivesical tissue (stage T3), and contiguous organs or tissues (stage T4)



  • Low-grade urothelial carcinoma when completely excised virtually never metastasizes



  • Despite the bland cytologic features, nested and large nested variants of urothelial carcinoma have well-documented metastatic potential



  • Pathologist must comment on whether the biopsy material contains muscularis propria (detrusor muscle) and also whether or not there is muscularis propria invasion



  • Superficial tumors have traditionally been treated with transurethral resection and intravesical chemotherapy or BCG, and muscle-invasive tumors have required radical cystectomy





Selected References




  • Chang A., Amin A., Gabrielson E., et. al.: Utility of GATA3 immunohistochemistry in differentiating urothelial carcinoma from prostate adenocarcinoma and squamous cell carcinomas of the uterine cervix, anus, and lung. Am J Surg Pathol 2012; 36: pp. 1472-1476.



  • Cox R., Epstein J.I.: Large nested variant of urothelial carcinoma: 23 cases mimicking von Brunn nests and inverted growth pattern of noninvasive papillary urothelial carcinoma. Am J Surg Pathol 2011; 35: pp. 1337-1342.



  • Magi-Galluzzi C., Zhou M., Epstein J.I.: Neoplasms of the urinary bladder.2007.Churchill LivingstonePhiladelphiapp. 176-189.



  • Samaratunga H., Delahunt B.: Recently described and unusual variants of urothelial carcinoma of the urinary bladder. Pathology 2012; 44: pp. 407-418.


Villous Adenoma


Clinical Features





  • Rare glandular neoplasm of the urinary bladder, which histologically mimics its enteric counterpart



  • The lesion occurs in elderly patients (mean age 65 years)



  • The most common locations are the urachus, dome, and trigone



  • Patients often present with hematuria or irritative symptoms, occasionally with mucosuria



  • Often coexists with in situ or invasive adenocarcinoma



Gross Features





  • Papillary tumor indistinguishable from papillary urothelial carcinoma



Histopathology





  • Blunt finger-like papillary architecture with central fibrovascular core, lined by pseudostratified columnar epithelium ( Figure 10.17A )




    Figure 10.17


    A, Villous adenoma. Neoplasm with blunt finger-like papillary architecture with central fibrovascular core, lined by pseudostratified columnar epithelium. B, Villous adenoma. Epithelial cells display nuclear stratification, crowding, hyperchromasia, and occasional prominent nucleoli.



  • Epithelial cells display nuclear stratification, crowding, hyperchromasia, and occasional prominent nucleoli ( Figure 10.17B )



Special Stains and Immunohistochemistry





  • CK20, CK7 and CEA: positive



  • Epithelial membrane antigen (EMA) and acid mucin stains: frequently positive



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Well-Differentiated Adenocarcinoma of the Colon or Bladder





  • Degree of cytologic atypia similar to analogous colonic lesions



  • Invasion into lamina propria



Pearls





  • Presence of villous adenoma histology in a limited biopsy does not entirely exclude the possibility of adenocarcinoma, and complete excision is essential





Selected References




  • Chan T.Y., Epstein J.I.: In situ adenocarcinoma of the bladder. Am J Surg Pathol 2001; 25: pp. 892-899.



  • Cheng L., Montironi R., Bostwick D.G.: Villous adenoma of the urinary tract: a report of 23 cases, including 8 with coexistent adenocarcinoma. Am J Surg Pathol 1999; 23: pp. 764-771.



  • Seibel J.L., Prasad S., Weiss R.E., et. al.: Villous adenoma of the urinary tract: a lesion frequently associated with malignancy. Hum Pathol 2002; 33: pp. 236-241.


Adenocarcinoma


Clinical Features





  • Rare bladder neoplasm comprising approximately less than 2% of all bladder tumors



  • Divided into two groups:




    • Nonurachal adenocarcinoma



    • Urachal adenocarcinoma




      • Accounts for two thirds of adenocarcinomas of the bladder



      • Found in adults with a mean age of 60 years



      • Most common presenting symptom is gross hematuria, followed by dysuria



      • Up to 40% of patients have metastatic disease at time of diagnosis



      • Occasionally associated with Schistosoma hematobium (less common association than with squamous cell carcinoma)



      • About 15% of tumors arise in patients with nonfunctioning bladder, and 85% are associated with exstrophy



      • Primary carcinoma derived from the urachal remnants



      • Occurs in the fifth or sixth decade; the mean patient age is 50 years



      • Mucosuria occurs in approximately 25% of cases





Gross Features


Nonurachal Adenocarcinoma





  • Typically an exophytic, papillary, ulcerating mass arising from the bladder mucosa



  • Usually involves the trigone or posterior bladder wall



  • Often shows infiltrative margins



  • May be sessile and cause a diffuse thickening of the bladder wall (resembles linitis plastica of the stomach); overlying bladder mucosa may be intact, leading to negative biopsies (signet ring cell variant)



Urachal Adenocarcinoma





  • Most form discrete masses over the dome of the bladder



  • It may involve urachal remnants, forming a large mass in the anterior abdominal wall



  • Overlying bladder mucosa may be intact or ulcerated



  • Cut surface of the mass often shows abundant mucin



Histopathology


Urachal and Nonurachal Adenocarcinomas





  • Mucinous carcinoma with pools of mucin containing single and groups of neoplastic cells (often resembles colonic adenocarcinoma)



  • Neoplastic glands with an infiltrative growth pattern



  • Glands are lined by large, pleomorphic cells with vesicular chromatin and prominent nucleoli; nuclear stratification is also common



  • Signet ring cells may be seen



  • CIS or intestinal metaplasia may be seen in nonurachal adenocarcinoma



Urachal Adenocarcinomas





  • Criteria to classify a tumor as urachal adenocarcinoma




    • Location in the dome or anterior wall of the bladder



    • Sharp demarcation between tumor and normal surface epithelium



    • Lack of urothelial carcinoma



    • Typically adjacent mucosa lacks prominent cystitis glandularis



    • Bulk of tumor is in the bladder wall rather than luminal



    • Exclusion of primary adenocarcinoma located elsewhere that has spread secondarily to the bladder




Special Stains and Immunohistochemistry





  • CK20, Leu M1 (CD15), and CEA: positive



  • CK7: variably positive



  • Villin: positive in the enteric type



  • CDX-2: frequently positive; nuclear staining for β-catenin: negative



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Cystitis Cystica et Glandularis





  • Small submucosal cysts with benign cytologic features



  • Typically small lesions without deep infiltration



Nephrogenic Adenoma





  • About 50% of cases found following genitourinary surgery



  • Composed of small uniform tubules resembling proximal tubules of the kidney



  • Usually much smaller than adenocarcinoma



Endometriosis





  • Composed of endometrial glands and stroma



  • Hemosiderin-laden macrophages often seen



Metastatic Adenocarcinoma





  • Presence of primary adenocarcinoma at distant site must be ruled out



Pearls





  • Intestinal metaplasia is the precursor lesion in most nonurachal adenocarcinomas



  • Treatment of urachal adenocarcinoma includes partial cystectomy with en bloc resection of the urachal ligament with the bladder dome and umbilicus



  • Treatment of nonurachal adenocarcinoma includes cystectomy or cystoprostatectomy with pelvic lymph node dissection



  • Overall prognosis is poor for both types





Selected References




  • Raspollini M.R., Nesi G., Baroni G., et. al.: Immunohistochemistry in the differential diagnosis between primary and secondary intestinal adenocarcinoma of the urinary bladder. Appl Immunohistochem Mol Morphol 2005; 13: pp. 358-362.



  • Siefker-Radtke A.: Urachal adenocarcinoma: a clinician’s guide for treatment. Semin Oncol 2012; 39: pp. 619-624.


Squamous Cell Carcinoma


Clinical Features





  • Can involve the urinary bladder, renal pelvis, or occasionally the ureter



  • Prevalence varies significantly depending on region of the world; it accounts for less than 5% of bladder carcinomas in areas where infection with Schistosoma haematobium is not endemic and 75% in areas where the infection is endemic



  • Associated with Schistosoma haematobium



  • Typically affects adults, with a slight male predominance



  • Patients typically have a long duration of symptoms of cystitis and often have gross hematuria



  • Bladder calculi and indwelling bladder catheters increase risk; tobacco is an important risk factor



Gross Pathology





  • Typically large solid tumors often filling the bladder lumen and infiltrating the bladder wall



  • Extensive necrosis is common



Histopathology





  • Well-differentiated form consists of well-defined islands of squamous cells with prominent intercellular bridges and minimal pleomorphism; keratin formation is typically abundant



  • Poorly differentiated form consists of sheets of neoplastic cells with marked cytologic atypia and focal squamous differentiation



  • Squamous metaplasia often seen in adjacent epithelium



  • Keratinizing squamous metaplasia or leukoplakia is often seen



Special Stains and Immunohistochemistry





  • MAC387, Desmoglein-3, TRIM29: positive



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Carcinoma with Squamous Differentiation





  • If urothelial component is present, the tumor should not be classified as a squamous cell carcinoma



  • Urothelial CIS may be seen; it would never be seen in a pure squamous cell carcinoma



Metastatic Squamous Cell Carcinoma





  • Presence of squamous cell carcinoma from local (cervix) or distant site must be ruled out



Squamous Papilloma





  • Lack of cytologic atypia and invasion



Condyloma





  • Presence of koilocytic cells



Pearls





  • It comprises approximately 5% of all malignant bladder tumors



  • The overall 5-year survival is 56%: 67% for patients with organ-confined tumor, and 19% for non-organ-confined tumor



  • Treatment consists of radical cystectomy or cystoprostatectomy



  • Overall poor prognosis



  • Commonly develop local recurrence rather than distant metastases



  • Metastases when present often involve bone





Selected References




  • Huang W., Williamson S.R., Rao Q., et. al.: Novel markers of squamous differentiation in the urinary bladder. Hum Pathol 2013; 44: pp. 1989-1997.



  • Kassouf W., Spiess P.E., Siefker-Radtke A., et. al.: Outcome and patterns of recurrence of nonbilharzial pure squamous cell carcinoma of the bladder: a contemporary review of The University of Texas M.D. Anderson Cancer Center experience. Cancer 2007; 110: pp. 764-769.


Small Cell Carcinoma


Clinical Features





  • Comprises less than 1% of primary bladder tumors



  • Typically found in elderly men, with a 4:1 male-to-female ratio



  • Most common presenting complaint is gross hematuria



  • Patients often have extensive local involvement or distant metastases at the time of presentation



Gross Pathology





  • Variable size, ranging from 2 cm to larger than 10 cm



  • May have solid or papillary architecture



  • Hemorrhage, necrosis, or mucosal ulceration are common



Histopathology





  • Resembles small cell carcinoma of other sites



  • Consists of uniform population of small to medium-sized cells with nuclear molding, scant cytoplasm, and nuclei with finely stippled chromatin and inconspicuous nucleoli



  • Nuclei are hyperchromatic and show prominent folding



  • Chromatin is dispersed, and nucleoli are inconspicuous



  • Mitotic activity and apoptosis are prominent



  • Diagnosis can be made on morphologic grounds alone, even if neuroendocrine differentiation cannot be demonstrated immunohistochemically



  • Rarely see well-differentiated variant, which has features of carcinoid, including an organoid pattern



Special Stains and Immunohistochemistry





  • Neuron-specific enolase (NSE), synaptophysin, and CD56: positive



  • Chromogranin: positive in one third of cases



  • Cytokeratin: typically positive; occasionally nonreactive



Other Techniques for Diagnosis





  • Electron microscopy: tumor cells contain numerous dense core neurosecretory granules



Differential Diagnosis


Metastatic Small Cell Carcinoma





  • Clinical correlation is needed to exclude presence of primary small cell carcinoma at distant site



  • Identification of urothelial component, including urothelial CIS, supports a bladder primary



Malignant Lymphoma





  • Consists of atypical lymphoid population



  • Positive staining for LCA



  • Negative staining for cytokeratin, synaptophysin, and chromogranin



Pearls





  • Aggressive behavior with poor prognosis



  • Overall 5-year survival rate for patients with local disease has been reported to be as low as 8%



  • Treatment includes radical cystectomy or cystoprostatectomy in addition to multiagent chemotherapy





Selected References




  • Moretto P., Wood L., Emmenegger U., et. al.: Management of small cell carcinoma of the bladder: consensus guidelines from the Canadian Association of Genitourinary Medical Oncologists (CAGMO). Can Urol Assoc J 2013; 7: pp. E44-E56.



  • Wang X., MacLennan G.T., Lopez-Beltran A., et. al.: Small cell carcinoma of the urinary bladder: histogenesis, genetics, diagnosis, biomarkers, treatment, and prognosis. Appl Immunohistochem Mol Morphol 2007; 15: pp. 8-18.



  • Zhao X., Flynn E.A.: Small cell carcinoma of the urinary bladder: a rare, aggressive neuroendocrine malignancy. Arch Pathol Lab Med 2012; 136: pp. 1451-1459.


Inflammatory Myofibroblastic Tumor/Inflammatory Pseudotumor


Clinical Features





  • Typically found in patients in second through fifth decades



  • Slightly more common in women



  • Usually presents with gross hematuria



Gross Pathology





  • Typically pedunculated, nodular mass ranging in size from 2 to 5 cm



  • May occasionally be sessile and extend into the underlying tissue



Histopathology





  • Characterized by myofibroblastic cells resembling tissue-culture fibroblasts arranged in fascicles or more haphazardly ( Figure 10.18 )




    Figure 10.18


    Inflammatory myofibroblastic tumor.

    The neoplasm is composed of a proliferation of spindle cells with a mixed inflammatory background.



  • Background usually contains a sparse inflammatory component consisting of lymphocytes and plasma cells; eosinophils may also be numerous



  • Prominent network of thin-walled blood vessels in an edematous or myxoid stroma with little-to-moderate collagen deposition is common



  • Spindle cells may show focal pleomorphism



  • Mitotic figures may be present and even frequent, but they are not atypical



  • Infiltration into the muscularis propria may occur



Special Stains and Immunohistochemistry





  • ALK protein: positive in two thirds of cases



  • Cytokeratin: variable staining pattern



  • Smooth muscle actin (SMA): often positive



  • Desmin: typically negative



Other Techniques for Diagnosis





  • Translocation involving chromosome 2p23, site of the ALK gene



Differential Diagnosis


Sarcomatoid Urothelial Carcinoma/Carcinosarcoma





  • Consists of malignant epithelial and malignant mesenchymal components



  • Numerous mitotic figures



  • Lacks inflammatory background



  • Lacks network of thin-walled blood vessels



Leiomyosarcoma





  • Overall, rare; however, it is the most common bladder sarcoma in older adults



  • Usually shows infiltrative margins



  • Typically shows cytologic atypia and increased mitotic activity with atypical mitotic figures



  • More commonly shows immunohistochemical evidence of smooth muscle differentiation



Pearls





  • Benign spindle cell neoplasm; complete surgical resection is the treatment of choice



  • Most common misdiagnosis is that of malignant sarcoma or sarcomatoid carcinoma



  • Most inflammatory pseudotumors are pedunculated and extend into the bladder lumen; occasionally they may be sessile and infiltrative





Selected References




  • Alquati S., Gira F.A., Bartoli V., et. al.: Low-grade myofibroblastic proliferations of the urinary bladder. Arch Pathol Lab Med 2013; 137: pp. 1117-1128.



  • Shanks J.H., Iczkowski K.A.: Spindle cell lesions of the bladder and urinary tract. Histopathology 2009; 55: pp. 491-504.



  • Sukov W.R., Cheville J.C., Carlson A.W., et. al.: Utility of ALK-1 protein expression and ALK rearrangements in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell lesions of the urinary bladder. Mod Pathol 2007; 20: pp. 592-603.



  • Young R.H.: Pseudotumors of the urinary bladder. Int J Surg Pathol 2010; 18: pp. 101S-105S.


Rhabdomyosarcoma


Clinical Features





  • Relatively common malignant neoplasm in children under the age of 15



  • Most common bladder tumor of childhood



  • Typically found before the age of 5



  • Slightly more common in boys (male-to-female ratio of 3:2)



  • Most tumors are of embryonal subtype and exophytic (polypoid), with or without a botryoid component



  • Rare in adults, usually of the pleomorphic type



  • Typically presents with hematuria or bladder outlet obstruction



Gross Pathology





  • Grossly, embryonal rhabdomyosarcoma can be divided into two basic forms with prognostic impact: polypoid, mostly intraluminal, associated with favorable prognosis (grapelike clusters, botryoid subtype); and deeply invasive tumors with a worse prognosis



  • Typically occurs at the bladder trigone



Histopathology





  • Tumor cells are small, round with scant cytoplasm, and hyperchromatic nuclei



  • Typically a loose myxoid background is seen



  • Large cells with abundant eosinophilic cytoplasm and cross-striations (strap cells) may be seen



Special Stains and Immunohistochemistry





  • Myogenin (myf4) and MyoD1: positive



  • Desmin and pan-actin (HHF35): positive, but not specific



  • Myosin and myoglobin: can be negative



  • Cytokeratin: negative



Other Techniques for Diagnosis





  • Electron microscopy: cells show thin actin and thick myosin filaments forming hexagonal pattern



Differential Diagnosis


Sarcomatoid Carcinoma (Carcinosarcoma)





  • Consists of malignant epithelial and malignant spindle cell components



  • Islands of cells with epithelial differentiation are seen



  • Cytokeratin positivity in the epithelial component



Inflammatory Myofibroblastic Tumor





  • Background usually contains a sparse inflammatory component



  • Prominent network of thin-walled blood vessels in an edematous or myxoid stroma



  • Mitotic figures may be present and even frequent, but they are not atypical



  • ALK-1 protein expression



Pearls





  • Treatment includes surgery, radiation therapy, and chemotherapy; combination therapy has greatly improved survival in the pediatric age group



  • Constitutes greater than 75% of bladder tumors in children



  • Most common mesenchymal tumor of the urinary bladder





Selected References




  • Sukov W.R., Cheville J.C., Carlson A.W., et. al.: Utility of ALK-1 protein expression and ALK rearrangements in distinguishing inflammatory myofibroblastic tumor from malignant spindle cell lesions of the urinary bladder. Mod Pathol 2007; 20: pp. 592-603.



  • Tavora F., Kryvenko O.N., Epstein J.I.: Mesenchymal tumours of the bladder and prostate: an update. Pathology 2013; 45: pp. 104-115.


Carcinosarcoma/Sarcomatoid Carcinoma With/Without Heterologous Elements


Clinical Features





  • Rare tumors of the urinary bladder



  • Primarily affects elderly adults (seventh and eighth decades)



  • Usually presents with hematuria or bladder outlet obstruction



  • May rarely involve the ureter, renal pelvis, and bladder diverticulum



  • Previous history of carcinoma treated by radiation or exposure to cyclophosphamide therapy is common



Gross Pathology





  • Typically large polypoid mass measuring up to 10 to 12 cm in diameter with infiltrative margins



Histopathology





  • Biphasic malignant neoplasm exhibiting morphologic or immunohistochemical evidence of epithelial and mesenchymal differentiation; presence or absence of heterologous elements should be mentioned in the diagnosis



  • Malignant epithelial component is composed of urothelial, glandular, or small cell component showing variable degree of differentiation



  • Mesenchymal component usually consists of pleomorphic, undifferentiated high-grade spindle cell neoplasm



  • Most common heterologous element is osteosarcoma followed by chondrosarcoma, rhabdomyosarcoma, leiomyosarcoma, liposarcoma



Special Stains and Immunohistochemistry





  • Cytokeratin (low molecular weight): epithelioid component is positive; some positivity in mesenchymal component may be seen



  • EMA may be positive but less frequently than cytokeratin



  • Vimentin: mesenchymal component is positive



  • SMA may be positive in areas of smooth or striated muscle differentiation



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis


Urothelial Carcinoma





  • Malignant urothelial cells without malignant spindle cell component



  • Vimentin negativity



Inflammatory Myofibroblastic Tumor/Postoperative Spindle Cell Nodule





  • Seen in association with recent therapeutic intervention, thus clinical history is important



  • Most involve the genital tract of women or periprostatic tissue of men



  • Reactive, highly cellular, spindle cell proliferation



  • Often shows myxoid background with scattered small blood vessels and sparse neutrophilic infiltrate



  • May have high mitotic rate; no abnormal mitoses



Malignant Spindle Cell Tumor, Including Leiomyosarcoma





  • Primary sarcoma of the bladder is rare in adults



  • Lacks epithelial component



  • Negative for cytokeratin and EMA



Pearls





  • Cytokeratin staining in both the epithelial and mesenchymal components supports a single cell line precursor theory



  • Epithelial component may represent a minority of the tumor, thus extensive sampling is required to identify an in situ or invasive epithelial component



  • Aggressive tumor with poor prognosis



  • Treatment consists of radical cystectomy or cystoprostatectomy; patients may also receive chemotherapy





Selected References




  • Cheng L., Zhang S., Alexander R., et. al.: Sarcomatoid carcinoma of the urinary bladder: the final common pathway of urothelial carcinoma dedifferentiation. Am J Surg Pathol 2011; 35: pp. e34-e46.



  • Gronau S., Menz C.K., Melzner I., et. al.: Immunohistomorphologic and molecular cytogenetic analysis of a carcinosarcoma of the urinary bladder. Virchows Arch 2002; 440: pp. 436-440.


Metastatic Tumors and Secondary Extension


Clinical Features





  • Metastases to the bladder or ureter are rare



  • Majority of metastatic lesions are secondary to direct extension from tumors of the prostate, lower intestinal tract, and female genital tract



  • Common primary tumors that metastasize to the bladder include breast, colon, or kidney carcinomas or malignant melanoma



Gross Pathology





  • Often multiple tumors, typically located in the submucosa



  • Focal ulceration of the urothelium overlying the mass may be seen



Histopathology





  • Typically located within the bladder wall in a submucosal location



  • Presence of a poorly differentiated tumor sparing the urothelial mucosa should raise suspicion of a possible metastasis



  • Glandular differentiation is typically seen in metastatic colonic carcinoma; gland formation may also be seen in metastatic prostate carcinoma



Special Stains and Immunohistochemistry





  • PSA, PSAP, p501s, NKX3.1: positive in metastatic prostate carcinoma



  • S-100, Melan A, and HMB-45: positive in metastatic melanoma



  • Villin, CDX-2: positive in metastatic colonic carcinoma



Other Techniques for Diagnosis





  • Noncontributory



Differential Diagnosis





  • Clinical history is important, especially the presence of a prostate carcinoma in men or a gynecologic tumor in women



Pearls





  • Bladder metastases are most frequently a late event and are almost always associated with disseminated disease



  • Patients typically have a poor prognosis





Selected References




  • Helpap B., Ayala A.G., Grignon D.J., et. al.: Metastatic tumors and secondary extension in urinary bladder: Tumors of the Urinary System and Male Genital Organs. WHO Classification of Tumors.2004.IARC PressLyonpp. 148-149.



  • Suh N., Yang X.J., Tretiakova M.S., et. al.: Value of CDX2, villin, and alpha-methylacyl coenzyme A racemase immunostain in the distinction between primary adenocarcinoma of the bladder and secondary colorectal adenocarcinoma. Mod Pathol 2005; 18: pp. 1217-1222.


Kidney


Renal Dysplasia


Clinical Features





  • Refers to presence of metanephric structures with aberrant nephronic differentiation



  • Two main theories have been considered in its pathogenesis: a primary failure of ureteric bud activity and a disruption produced by fetal urinary flow impairment



  • Most often sporadic, but may be syndromic and develop as part of a multiple malformation syndrome or chromosomal anomaly, some of which are hereditary



  • Almost always accompanied by other urinary tract abnormalities



  • Dysplastic kidneys are usually nonfunctional



  • Large cystic dysplastic kidneys typically present as a palpable mass in a newborn; diagnosis confirmed by ultrasound



  • Small dysplastic kidneys may remain asymptomatic for many years



  • Bilateral disease results in oligohydramnios (Potter syndrome), and neonatal death from pulmonary hypoplasia



Gross Pathology





  • Unilateral or bilateral involvement may be seen



  • Distorted renal parenchyma with numerous variably sized cysts



  • Dysplastic kidneys are usually enlarged; may occasionally be small



Histopathology





  • Characteristic features include markedly disorganized kidney parenchyma with islands of cartilage and dysplastic ducts lined with columnar epithelium and surrounded by collars of spindle cells ( Figure 10.19B )




    Figure 10.19


    A, Renal dysplasia. Island of cartilage and cystic spaces lined by flattened epithelium. Few glomeruli are seen. B, Renal dysplasia. Markedly disorganized kidney parenchyma with dysplastic ducts lined with columnar epithelium and surrounded by collars of spindle cells.



  • Cystic spaces lined by flattened epithelium ( Figure 10.19A )



  • Rudimentary glomeruli may be seen



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • If multiple malformations are detected in a pediatric autopsy, it is important to obtain tissue for karyotype analysis



Differential Diagnosis


Infantile Polycystic Kidney Disease (Autosomal Recessive)





  • Often results in stillbirth or early neonatal death



  • Cysts are in the cortex and medulla and do not congregate at the papillary tips



  • Cartilaginous metaplasia or other dysplastic elements never seen



  • Normal-appearing nephrons in the cystic areas



Medullary Cystic Disease (Autosomal Dominant)





  • Patients present with renal failure in first or second decade



  • Cysts are located at the corticomedullary junction



Medullary Sponge kidney





  • Sporadic; typically found in children or adolescents; not found at birth



  • Ectasia of the papillary collecting ducts of one or more renal pyramids



  • Renal function is normal



  • Rare progression to end-stage renal disease



Cystic renal neoplasm





  • Fibrous capsule separating the cystic lesion and normal kidney



  • No nephronic structures in the cystic septa



Pearls





  • Usually associated with congenital genitourinary abnormalities, including ureteral atresia



  • Many investigators believe that renal dysplasia is associated with in utero urinary tract obstruction



  • Unilateral disease is typically treated by nephrectomy



  • Bilateral renal dysplasia ultimately results in renal failure





Selected References




  • Chen R.Y., Chang H.: Renal dysplasia. Arch Pathol Lab Med 2015; 139: pp. 547-551.



  • Woolf A.S., Price K.L., Scambler P.J., et. al.: Evolving concepts in human renal dysplasia. J Am Soc Nephrol 2004; 15: pp. 998-1007.


Infantile (Autosomal Recessive) Polycystic Kidney Disease


Clinical Features





  • Found in 1/10,000 to 1/50,000 live births



  • Usually results in stillbirth or early neonatal death



  • Abdominal distention due to massively enlarged kidneys



  • Lungs may be poorly developed and hypoplastic owing to compression of the thoracic organs; fatal in 75% of cases



  • Associated with congenital hepatic fibrosis in patients who survive infancy



Gross Pathology





  • Always bilateral disease



  • Massively enlarged kidneys with smooth external surface



  • Renal parenchyma shows numerous small cysts involving the cortex and medulla



  • Cysts are radially arranged and are oriented perpendicular to the renal capsule



  • Calyceal system is normal



Histopathology





  • Dilated collecting ducts lined by uniform cuboidal cells ( Figure 10.20 )




    Figure 10.20


    Infantile polycystic kidney.

    Characteristic dilated collecting ducts located perpendicular to the renal capsule.



  • Normal-appearing nephrons between cysts



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Cytogenetic studies: associated with single gene (PKHD1) mutation on chromosome 6p21-23: encodes for polyductin/fibrocystin



Differential Diagnosis


Dysplastic Kidney





  • Markedly disorganized kidney parenchyma with islands of cartilage and dysplastic ducts lined with columnar epithelium and surrounded by collars of spindle cells



Medullary Cystic Disease





  • Presents with renal failure in first or second decade



  • Patients have polyuria and polydipsia as a result of salt wasting; develop uremia and growth retardation



  • Kidneys are typically small; bilateral disease



  • Cysts are numerous, less than 2 cm in diameter and located primarily at the corticomedullary junction



  • Most patients develop end-stage renal disease within 5 years of diagnosis



Medullary Sponge Kidney





  • Typically found in children or adolescents; not found at birth



  • Kidneys are typically of normal size



  • Multiple small cysts (<0.5 cm) that involve the medullary pyramids and renal papillae and communicate with the collecting ducts



  • Rare progression to end-stage kidney disease



Pearls





  • Autosomal recessive disease



  • Poor prognosis; often causes death in utero or shortly after birth



  • Most cases are associated with multiple epithelium-lined cysts in the liver





Selected References




  • Bergmann C.: Genetics of autosomal recessive polycystic kidney disease and its differential diagnoses. Front Pediatr 2018; 9: pp. 221.



  • Dell K.M.: The spectrum of polycystic kidney disease in children. Adv Chronic Kidney Dis 2011; 18: pp. 339-347.


Adult (Autosomal Dominant) Polycystic Kidney Disease


Clinical Features





  • Found in 1/400 to 1/1000 live births



  • One of the leading causes of end-stage renal disease in adults; found in 5% to 10% of all patients on dialysis



  • Family history in approximately 70% to 75% of affected persons



  • Typically presents in fourth to fifth decade after sufficient renal parenchyma destruction has occurred and renal failure has developed



  • Usually presents with hematuria (secondary to stones, tumor, or infection) or proteinuria



  • Chronic flank pain is common



  • Patients often develop urinary tract infections



  • Extrarenal manifestations



  • Intracranial Berry aneurysms, hypertension, colonic diverticula, extrarenal cysts (pancreatic, hepatic), and cardiac valve abnormalities including mitral valve prolapse



Gross Pathology





  • Early in the disease, kidneys are normal sized with few cysts in cortex and medulla



  • Progression of disease leads to marked bilateral kidney enlargement with an increase in the size and number of cysts (may weigh up to 4 kg each) ( Figure 10.21A )




    Figure 10.21


    A, Adult polycystic kidney. Grossly the kidneys are markedly enlarged and show numerous cysts in the cortex and medulla. B, Adult polycystic kidney. Multiple cysts are lined by flat cuboidal epithelium, some of which contain proteinaceous material.



  • Kidneys have irregular contour due to numerous peripheral cysts



  • Cysts range in size from few millimeters up to several centimeters; typically contain hemorrhagic or clear yellow fluid



Histopathology





  • Cysts are lined by single layer of flat to cuboidal epithelium ( Figure 10.21B )



  • Small papillary projections may be seen



  • Cysts contain proteinaceous material; calcified deposits are often seen



  • Intervening kidney tissue typically shows interstitial fibrosis, lymphocytic infiltrate, tubular atrophy, and glomerular and vascular sclerosis



  • Frequently associated with renal epithelial tumors (renal cell carcinoma)



Special Stains and Immunohistochemistry





  • Noncontributory



Other Techniques for Diagnosis





  • Cytogenetic studies:




    • Abnormality associated with chromosome 16 (16q13.3) in 85% of patients (involves PKD1 gene, which encodes a protein named polycystin 1)



    • Associated with mutations in PKD2 gene on chromosome 4 (4q21-23), which encodes polycystin 2 in approximately 15% of cases




Differential Diagnosis


Acquired Cystic Disease





  • Patients typically have chronic renal failure and are on dialysis before cysts develop



  • Kidney size reduced or only moderately enlarged



  • Cysts are typically located in the cortex



  • Lacks family history, which is typically present in polycystic kidney disease



  • No associated extrarenal manifestations



Pearls





  • Autosomal dominant disorder with high penetrance



  • Almost 100% penetrance if patient lives to 80 years of age



  • End-stage kidney disease is found in approximately 50% of patients by age 60



  • The main and most effective therapy remains control of hypertension by renin-angiotensin-aldosterone system (RAAS) blockade



  • Renal transplant is curative when patient develops end-stage kidney disease





Selected References




  • Bergmann C.: Genetics of autosomal recessive polycystic kidney disease and its differential diagnoses. Front Pediatr 2018; 9: pp. 221.



  • Gimpel C., Bergmann C., Bockenhauer D., et. al.: International consensus statement on the diagnosis and management of autosomal dominant polycystic kidney disease in children and young people. Nat Rev Nephrol 2019; 15: pp. 713-726.


Acquired Cystic Disease


Clinical Features





  • Common finding in patients receiving hemodialysis or peritoneal dialysis



  • Presence of cysts increases as time on dialysis increases



  • Occasionally seen in patients with chronic renal insufficiency who are not on dialysis



  • Pathogenesis of cyst formation remains largely unknown



  • Often remains asymptomatic; may present with gross or microscopic hematuria



  • Cyst formation is associated with increased risk of RCC



Gross Pathology



Mar 11, 2021 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Ureter, Urinary Bladder, and Kidney
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