Other Tumors and Tumor-like Lesions of the Renal Pelvis

Other Tumors and Tumor-like Lesions of the Renal Pelvis

Satish K. Tickoo, MD

Victor E. Reuter, MD

All aberrant morphologies of urothelial carcinoma seen in the bladder may be seen in the upper tract. Adenocarcinomas may be pure but often appear in association with a urothelial component image.

Squamous cell carcinoma, seen here invading the renal parenchyma image, is the 2nd most common carcinoma in the pelvis. Most cases occur as aberrant differentiation in UC, but pure forms may be seen.



  • Neoplasms other than usual urothelial carcinoma involving upper urinary tract


Nephrolithiasis and Repeated Infections

  • Squamous cell carcinoma and adenocarcinoma often occur in background of nephrolithiasis

    • Reported incidence of coexisting calculus disease in squamous cell carcinoma of renal pelvis varies from 18-100%

      • Squamous cell carcinoma is often associated with squamous metaplasia of urothelium

    • Adenocarcinoma is usually associated with intestinal metaplasia, which is regarded as putative precursor of adenocarcinoma

Bladder Cancer

  • Most cases of renal pelvic urothelial (transitional cell) carcinoma are associated with prior, concurrent, or subsequent bladder carcinoma

  • However, for nontransitional cell carcinomas of upper tract, such association is not observed



  • Incidence

    • Most carcinomas with nontransitional cell features in pelvis coexist with usual urothelial (transitional cell) carcinomas of pelvis

    • Pure nonurothelial carcinomas of renal pelvis are very rare

      • Squamous cell carcinoma is 2nd most common carcinoma of renal pelvis

      • Incidence of 10% of renal pelvic cases is reported in older study; likely includes urothelial carcinomas with squamous differentiation

      • More recent studies report a combined incidence of < 1% for squamous cell carcinomas and adenocarcinomas of renal pelvis

      • All other types of carcinoma in the literature exist as case reports or small case series

    • Benign epithelial, mesenchymal, and other tumors are also very rare

      • Fibroepithelial polyps, although more common in adults, are most common benign polypoid ureteric tumors in children

  • Age

    • Carcinomas: Range 41-87 years (mean: 66)

    • Fibroepithelial polyps: Range 7-73 years (mean: 40)

    • Inverted papillomas: Range 19-89 years (mean: 64)

    • Primitive neuroectodermal tumors: Mostly young adults/adolescents; range 10-60 years (mean: 27)

    • Other tumors: Variable, mostly older adults


  • Flank pain &/or hematuria common presentations

  • Ureteral or pelvi-ureteric junction obstruction with resultant hydronephrosis also not uncommon

  • Episodic colicky pain, especially in tumors of ureter


  • Surgical approaches

    • Usually nephroureterectomy performed for carcinomas of pelvis or proximal-most ureter

    • Malignant tumors of more distal ureters may be amenable to ureterectomy

    • Polypoid smaller benign tumors, particularly fibroepithelial polyps, may be resected endoscopically


  • Most pure nontransitional cell, as well as urothelial carcinomas with divergent/aberrant differentiation, are high-grade and high-stage tumors

  • Most patients with pT3 or pT4 tumors die of disease, and 5-year survivals are extremely uncommon

  • Some of benign tumors may cause obstruction and resultant hydronephrosis, with related complications


General Features

  • Carcinomas

    • Usually large bulky tumors, filling pelvicalyceal system, usually with renal parenchymal and renal sinus soft tissue invasion

  • Fibroepithelial polyps, hemangiomas, squamous papillomas, and nephrogenic adenomas

    • Mostly polypoid lesions in pelvis or ureter

    • Size usually small (mean: 2 cm; mostly 0.5-4 cm in maximum diameter); rare tumors are much larger

  • Inverted papillomas

    • Smooth surfaced and often broad based, sessile and domed, rarely pedunculated

      • More common in ureter than pelvis

  • Malignant mesenchymal tumors

    • Often arising in perirenal and renal hilar soft tissues, and secondarily involving pelvicalyceal system and renal parenchyma


Histologic Features

  • Benign epithelial tumors/lesions

    • Inverted papilloma

      • Endophytic interconnected trabeculae and cords of urothelium, extensively invaginating from surface into lamina propria

      • Covered by flat-surfaced urothelium

      • Periphery of cords typically show palisading of basal nuclei

      • Tumor periphery is smooth and pushing, and no desmoplastic stromal reaction is present

      • Some cases show small glandular structures lined by metaplastic mucinous epithelium

    • Nephrogenic metaplasia/adenoma

      • Shows wide spectrum of architectural patterns, with cases often showing mixed patterns

      • Architectural patterns include papillary, tubular/glandular, cystic, single cells, and sheet-like

      • Lining epithelial cells are cuboidal and single layered, or occasionally “hobnailed”

      • Cytoplasm varies from eosinophilic to clear; prominent nucleoli may be present

      • In single cell areas, cells may show minute lumina, and closely mimic blood vessels or signet ring cells

      • Typically, thick basement membrane/hyalinized sheath surrounds epithelium

      • Often associated with inflammatory infiltrate

    • Villous adenoma

      • Similar to villous adenomas of colorectum

      • Biopsy-based diagnosis of villous adenoma should not be made, as adenocarcinoma in vicinity may be missed

      • Until thorough evaluation of completely excised resection specimen performed, terminology, such as “biopsy fragments with histology of at least villous adenoma,” may be used

    • Other rare benign epithelial lesions include squamous and urothelial papillomas

  • Malignant epithelial tumors

    • Squamous cell carcinoma

      • More common in renal pelvis than ureter; often associated with nephrolithiasis

      • Usually accompanied by extensive squamous metaplasia of urothelium and squamous cell carcinoma in situ

      • Often high stage, frequently with renal parenchymal invasion

    • Adenocarcinoma

      • Variety of morphologic phenotypes seen, similar to that in bladder

      • Different morphologic forms include glandular NOS, enteric, signet ring, mucinous

      • Often accompanied by glandular and intestinal metaplasia of surrounding urothelium, or occasionally by villous adenoma

      • Usually high-stage tumors, often with renal parenchymal invasion

    • Other rare forms of carcinoma (Ca) include

      • Small cell and large cell neuroendocrine Ca, lymphoepithelioma-like Ca, sarcomatoid Ca, hepatoid Ca, rhabdoid Ca, and lipid-rich Ca

  • Benign nonepithelial tumors/lesions

Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Other Tumors and Tumor-like Lesions of the Renal Pelvis

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