Polyoma virus-associated cellular changes in the urine and bladder biopsy samples: a cytohistologic correlation

Polyoma (BK) virus-type cellular changes are occasionally reported in urine specimens, yet rarely detected in histologic sections of bladder biopsies. A total of 762 predominantly voided urine specimens with a cytologic diagnosis of polyoma virus-type change were retrieved from the cytopathology files of the Johns Hopkins Hospital over a 15-year period (1988-2003). Biopsies were available for 33 cases (29 patients) following or preceding the urinary cytology (mean interval, 210 days). The biopsies originated primarily from bladder (n=31) with one biopsy each from renal pelvis and urethra. Representative paraffin blocks were chosen from each case for immunoperoxidase staining with SV40 large T antigen. There were 22 males and 7 females with an age range of 34 to 79 years (mean, 64.7 years). The histologic diagnoses of the 33 tissue biopsies were: benign urothelium (n=9), urothelial carcinoma (n=21) and 1 case each of dysplasia, small cell carcinoma, and chronic lymphocytic leukemia involving lamina propria of the bladder. Only 3 of 33 biopsies on hematoxylin-stained sections showed morphologic changes of polyoma virus, which lacked sufficient tissue to perform immunohistochemistry for SV40 large T antigen (LTag). Immunohistochemical staining for LTag was positive in 7 cases. Only 2 cases showed strong/diffuse and moderate/focal staining for LTag with both representing invasive high-grade urothelial carcinoma (where no inclusions were seen on hematoxylin and eosin-stained sections) and both demonstrating positive immunostaining for p53. One of these 2 cases was from an organ transplant recipient and the other from a patient with no known immunosuppression. Our data lead to the following conclusions: 1) cytology appears to be more sensitive than histology in detecting cells with polyoma virus; 2) cytohistologic discordance might be due to: a) polyoma (BK) virus infected cells are shed from the tissue and collected in the urine; b) polyoma virus changes may be focal and not sampled in directed tissue biopsies; c) polyoma virus changes may originate from sites in the genitourinary tract other than the bladder; d) the lack of a "gold standard" to confirm the cytologic diagnoses of polyoma virus; and e) the discordance in time between the biopsy and cytology specimens in the current retrospective study. 3) Because some cytologically benign cases of polyoma virus were associated with malignant biopsies, careful morphologic evaluation is required to avoid false-negative urinary cytology samples. This investigation further examined the immunohistochemical staining pattern for SV40 LTag and p53 in noninvasive low-grade papillary urothelial carcinoma using a tissue microarray constructed from bladder biopsies of 79 randomly selected patients. Weak LTag staining was present in occasional neoplastic urothelial cells of 2 patients. The staining was present in only one of four samples from each tumor (0.63%; 2 of 316 tumor spots), which further illustrates the patchy and focal presence of virion containing cells. p53 staining in these two spots was also patchy and confined to rare nuclei.