Catheterised specimens are collected for a variety of reasons, such as the work-up of patients who may have a urinary tract infection, determining the cause of haematuria, or for cancer screening in patients who have in-dwelling catheters.

A washing may be performed of any part of the urinary tract, although the most common washing specimen is of the bladder. Washing specimens may be directed or undirected and in a washing procedure, a solution (e.g. electrolyte or saline) is injected into the cavity of interest and then withdrawn. Washing specimens are often performed as a method for examining a large area for cancer. Washings are the most sensitive cytological method for cancer detection. Upper tract specimens are a type of washing specimen, but often are discussed separately because the cytological findings of the upper tract differ from those of the bladder, the upper tract consisting of the renal collecting ducts, pelves and ureters.

A brushing is performed under cystoscopic guidance of a specific area of concern. Brushing sampling may be performed on any portion of the urinary tract and are often collected in conjunction with a washing. The brushing specimen is either placed directly on a slide or placed into a fixative.

Voided urine specimens sample the entire urinary tract, including the kidneys, renal pelves, ureters, bladder and urethra. As these urinary tract regions may be lined by different cell types, voided urine specimens from a non-diseased tract may exhibit a variety of appearances, reflecting the fact that different portions of the urinary tract are lined by urothelial cells, squamous cells, and glandular cells.

Urothelial cells. Like squamous epithelium, urothelium is divided into three cell layers: superficial, intermediate and basal/parabasal. Urothelium varies in thickness from two to three cells in the renal pelvis to five to six in the bladder (Fig. 12.1). The superficial urothelial cell layer is a single cell in thickness and superficial cells are large, sometimes multinucleated, and also known as umbrella cells because of their contours. Superficial urothelial cells may be larger than 100 μm in diameter, although their nuclear to cytoplasmic ratio is low, except in reactive conditions or in degenerate specimens. Most superficial cells contain from one to three nuclei, although it is not unusual to see more nuclei, as these cells respond to a variety of insults. Overall, a superficial urothelial cell is approximately the size of an intermediate squamous cell. The cytoplasm of superficial cells is variable, but tends to be finely granular (Fig. 12.2); cytoplasmic vacuolation is fairly common, especially in reparative processes. The cytoplasmic borders are well defined and the cells have a rounded appearance. Superficial cells are the most common urothelial cell type seen in voided urine specimens from non-diseased individuals. Seeing cells from other urothelial layers is a sign of disease in a voided urine specimen.

Fig. 12.1 Histology: section of bladder. A full-thickness section of reactive urothelium is shown. The superficial urothelial cells show abundant cytoplasm, large nuclei and prominent nucleoli. Several of the superficial cells show multinucleation (H&E).

Fig. 12.2 Urine, voided: superficial cells. Several large multinucleated superficial cells with abundant cytoplasm are admixed with inflammatory cells and debris. The superficial cell nuclei are enlarged and lack significant hyperchromasia. A few of these nuclei contain a prominent nucleolus (PAP).

The intermediate cell layer is variable in thickness and the cells are cuboidal and much smaller than intact superficial cells. The basal/parabasal cell layer also is a single layer in thickness and the cells are a similar shape but slightly smaller compared to intermediate urothelial cells (Fig. 12.3).

Fig. 12.3 Urine, wash: intermediate, basal, and parabasal cells. Intermediate, basal and parabasal urothelial cells are considerably smaller than superficial cells and contain a small to moderate amount of cyanophilic cytoplasm that is finely vacuolated. Their nuclei are round to oval and may also contain a prominent nucleolus in reactive processes. The nuclei shown here are about twice the size of red blood cells (PAP).

Squamous cells. The female urethra is entirely lined by stratified squamous epithelium, and the male urethra is lined by stratified squamous epithelium at the orifice of the penile (spongy) portion. The remainder of the penile portion and the membranous portion are lined partially by stratified squamous epithelium and partially by urothelium. Squamous epithelium also may be found in the bladder, and is normally seen in the trigone in 10% of men and 50% of women.¹¹ In voided urine specimens, superficial squamous cells from the urothelial tract may be present (Fig. 12.4). In women, the urinary tract squamous cells are often confused with benign squamous cell contaminant from the gynecological tract. The presence of bacteria associated with squames, in the absence of reactive changes and inflammation, is usually a sign that the squamous cells are not of urinary tract origin (Fig. 12.5).

Fig. 12.4 Urine, voided: benign squamous cells. Three superficial squamous cells with small nuclei and abundant cytoplasm are admixed with a few inflammatory cells. This voided urine is from a man who has a history of lithiasis (PAP).

Fig. 12.5 Urine, voided: squamous cell contaminant. In this voided urine from a 45-year-old woman with haematuria, squamous cells are admixed with abundant bacteria. There is an absence of acute inflammation. Note the single, slightly degenerate, reactive urothelial cell with densely granular nuclear chromatin (PAP).

Glandular cells. Glandular cells are more frequently seen in instrumented urine specimens and have a number of sources (Box 12.2).^12,13 Most glandular cells arise from the urothelial lining itself, as the urothelium is capable of differentiating along several pathways. Glandular epithelium also may arise as a response to chronic irritation. Mucous-secreting glands are normally found in the spongy portion of the male urethra and in the female urethra, hence these cells may be shed in voided urine specimens. Glandular cells exhibit oval, basal nuclei with finely granular blue to green cytoplasm. Cytoplasmic vacuolation and even cilia may be seen. Renal tubular cells are observed in casts or small sheets and reflect kidney disease such as infarct or tubular necrosis.

A variety of cells other than urothelial, squamous and glandular cells and other structures may be seen in voided urine specimens. These cells include inflammatory cells, red blood cells (Fig. 12.6) and sperm. Other structures include crystals (Fig. 12.7), casts (Fig. 12.8) and corpora amylacea.

Fig. 12.6 Urine, voided: inflammatory cells and red cells. Acute inflammatory cells are admixed with red cells and several reactive urothelial cells. The nuclei in the superficial urothelial cell show degenerative features with foci of nuclear membrane thickening and breaks (PAP).

Fig. 12.7 Urine, voided: crystals. A large superficial urothelial cell is adjacent to a large crystal. Red blood cells and debris are present in the background (PAP).

Fig. 12.8 Urine, voided: cast. A renal tubular cast is admixed with crystals and a reactive intermediate urothelial cell (PAP).

Instrumented specimens are characterised by high cellularity, as the method of cellular procurement forcibly removes epithelium (Fig. 12.9). These specimens show large groups of cells, small cell clusters and single cells from all urothelial cell layers. The large groups of urothelial cells often demonstrate all cell layers, with superficial cells overlying intermediate and basal/parabasal cells (Fig. 12.10). These groups are termed ‘instrumentation artefact’ and may be confused with low-grade urothelial carcinomas.¹⁴ At high power, the smaller groups of urothelial cells lack significant atypia (Fig. 12.11).

Fig. 12.9 Urine, washing: high cellularity. At a low power, this bladder washing specimen in a patient with a history of lithiasis shows a variety of urothelial cell types. Superficial and intermediate urothelial cells are admixed with inflammatory cells and squamous cells (PAP).

Fig. 12.10 Urine, washing: three-dimensional cell group. A large staghorn cluster of urothelial cells is infiltrated by a few acute and chronic inflammatory cells. The urothelial cell nuclei are round to oval and contain thickened nuclear rims, although the chromatin pattern is hypochromatic. A small red nucleolus is present in most of the nuclei. The urothelial cell cytoplasm is finely granular and not homogeneous (PAP).

Fig. 12.11 Urine, washing: benign urothelial cells. A three-dimensional group of urothelial cells shows round nuclei with evenly distributed granular nuclear chromatin. Although the nuclei show overlapping, other characteristics of neoplasia are lacking (PAP).

Catheterised urines tend to show more inflammation than other instrumented urine types, as indwelling catheters cause irritation and inflammation (Fig. 12.12).

Fig. 12.12 Urine, catheterised: acute inflammation. This patient has an indwelling catheter and a secondary infection, characterised by marked acute inflammation. A reactive superficial cell with a moderate amount of cytoplasm showing bichromasia is present (PAP).

Ileal conduit specimens are predominantly composed of numerous intestinal glandular cells and inflammatory cells that often have a degenerate appearance (Fig. 12.13).^15,16 The high cellularity arises from the natural sloughing of the intestinal epithelium, as glandular cells lack the hardiness to withstand the toxicity of urine. The glandular cells may form flat sheets, similar to the findings in colonic brushing specimens. The degenerate glandular cells contain a pyknotic and eccentrically placed nucleus. The nuclear to cytoplasmic ratios are not increased, but the smudged hyperchromasia may be alarming. Occasional upper tract superficial urothelial cells are seen.

Fig. 12.13 Urine, ileal conduit: degenerate cells. Most ileal conduit urines are cellular and contain few urothelial cells, abundant degenerate glandular cells, and debris. The degenerate ileal cells contain small, hyperchromatic nuclei and a moderate amount of cytoplasm (PAP).

The malignant cells of a high-grade urothelial carcinoma are generally observed singly, although loose clusters also may be present.^24,34 In voided urines, only rare cells may be seen, indicating that careful screening, as for cervical smear tests, is necessary.

The malignant cells vary in size and shape, and in some cases, huge malignant cells may be seen (Fig. 12.14). The nuclear:cytoplasmic ratio is increased, and most malignant cells have only a thin rim of dense, homogeneous or non-vacuolated cytoplasm (Fig. 12.15).³² Cytoplasmic vacuolation is not a typical feature, but may be observed in cases with abundant acute inflammation. The cytoplasmic membranes are easily distinguished in high-grade urothelial carcinomas.

Fig. 12.14 Urine, voided: high-grade urothelial carcinoma. The malignant urothelial cells vary in size and shape and exhibit variable degrees of degeneration. A large atypical mitotic figure is seen in the centre of the field (PAP).

Fig. 12.15 Urine, voided: high-grade urothelial carcinoma. The malignant urothelial cells contain a thin rim of homogeneous cytoplasm. There is an absence of cytoplasmic vacuoles (PAP).

The appearance of the nucleus is the defining feature of high-grade urothelial carcinoma. The nucleus is large and exhibits marked nuclear membrane irregularities (Fig. 12.16). The nuclear chromatin is extremely coarse and some cells have a West Virginia ‘coal black’ appearance, indicating that the chromatin is uniformly dark and impenetrable in appearance due to degenerative changes (Fig. 12.17).^32,35 When present, nucleoli are large and prominent and cytophagocytosis may be present (Fig. 12.18).³⁶ Nassar et al. reported that greater smudging of cancer cells was observed in monolayer preparations, although monolayer preparations also showed more even disbursement of malignant cells.³⁷

Fig. 12.16 Urine, voided: high-grade urothelial carcinoma. The malignant cell nuclei are large and the nuclear membranes are irregular. The nuclear membranes show focal thickening. Several of the nuclei show multiple prominent nucleoli (PAP).

Fig. 12.17 Urine, voided: high-grade urothelial carcinoma. Occasional malignant urothelial cell nuclei have a ‘coal black’ appearance with densely hyperchromatic chromatin patterns (PAP).

Fig. 12.18 Urine, voided: high-grade urothelial carcinoma. The malignant urothelial cell nuclei are large and prominent nucleoli are seen (PAP).

High-grade urothelial carcinomas occasionally exhibit squamous or glandular differentiation, squamous being the more frequent (Fig. 12.19).²³ Squamous differentiation is characterised by keratinisation, sometimes manifested by parakeratosis or keratin pearls (Fig. 12.20). Malignant glandular differentiation is difficult to recognise but is discernible by cytoplasmic vacuolation. Although invasive high-grade urothelial carcinomas may exhibit sarcomatoid differentiation, the malignant cells are not typically observed in voided urine specimens but may be seen in washing specimens (Fig. 12.21).

Fig. 12.19 Urine, voided: high-grade urothelial carcinoma. The malignant cells show glandular differentiation with finely vacuolated cytoplasm, similar to the cytoplasmic presentation seen in clear cell carcinoma of the kidney. A multinucleated malignant urothelial cell with densely homogeneous cytoplasm is present in the center of the group of malignant cells showing glandular differentiation (PAP).

Fig. 12.20 Urine, voided: high-grade urothelial carcinoma. Several of the malignant cells show squamous differentiation. Note the presence of a malignant urothelial cell showing dense cytoplasm without keratinisation (PAP).

Fig. 12.21 Urine, washing: high-grade urothelial carcinoma. The malignant cells show a spindled appearance consistent with low-grade sarcomatous differentiation. The malignant spindle cells have densely hyperchromatic nuclei that vary in size and shape. The degree of mesenchymal differentiation may vary considerably. There is an absence of inflammation in the background (PAP).

High-grade urothelial carcinoma cells tend to be few and are admixed with the numerous degenerate glandular cells, as described above. The malignant cells often are better preserved, are larger, and maintain crisper nuclear membranes, compared to the degenerate cells (Fig. 12.22).^15,16

Fig. 12.22 Urine, ileal conduit: high-grade urothelial carcinoma. The malignant cells show non-degenerate features in a background of degenerate ileal cells. The size of the malignant urothelial cell nuclei is considerably larger than the degenerate glandular cell nuclei (PAP).

In instrumented urine specimens, numerous malignant cells usually are seen (Fig. 12.23) and the malignant cells have the same cytological features as described for voided urine specimens. Small- to moderate-sized clusters of malignant cells may be seen, but large groups of malignant cells are unusual, as high-grade urothelial carcinomas typically show extensive cellular dissociation.

Fig. 12.23 Urine, washing: high-grade urothelial carcinoma. The malignant cells are numerous and pleomorphic. Tumour diathesis and debris are admixed with malignant cell nuclei showing a coal black appearance (PAP).

Benign urothelial cells of the upper tract, compared with their lower tract counterparts, show higher nuclear:cytoplasmic ratios, more prominent nuclear membrane irregularities and larger nuclei (Fig. 12.24). Instrumentation produces large groups of cells. Nonetheless, the diagnosis of high-grade urothelial carcinoma tends to be straightforward, as the nuclear size, hyperchromasia and membrane irregularities exceed the changes of benign urothelium.^38–40 Potts et al reported that the criteria of high nuclear:cytoplasmic ratios, anisonucleosis and nuclear overlapping were among the most important criteria in diagnosing high-grade urothelial carcinoma of the upper tract (Fig. 12.25).⁴¹

Fig. 12.24 Urine, upper tract: high-grade urothelial carcinoma. The malignant cells show marked nuclear atypia in a background of slightly atypical urothelial cells (PAP).

Stay updated, free articles. Join our Telegram channel

Join