[Proliferating character of inverted papilloma of the urinary bladder]

Inverted papilloma (IP) of the urinary bladder is generally considered to be a benign lesion by histological examination. In recent years, however, there have been several cases of IP simultaneously accompanied with transitional cell carcinoma (TCC), elsewhere in the bladder or combined as a single urothelial lesion. So we investigated proliferating character of IP by DNA ploidy analysis and immunohistostaining with proliferating cell nuclear antigen (PCNA).

Six cases of IP of the urinary bladder were analyzed and 12 cases of TCC of G1 and G3 grade were included in this study as a control. As DNA ploidy analysis, all specimens were feulgen stained using CAS DNA staining kit and examined by image cytometry (CAS 200R system). For the PCNA immunohistochemistry, all specimens were stained with anti-PCNA monoclonal antibody (Novocastra Lab.: PC10) according to ABC (avidin-biotin-complex) standard method. We determined that the DNA Index of the case under 1.20 was diploid and the others was aneuploid. PCNA staining were determined by only one pathologist as follows: negative (-) and positive (+), (2+) and (3+).

As DNA ploidy, 5 of 6 cases of TCC G3 group as a control were aneuploid. But in spite of all cases of TCC G1 group were diploid, among IP cases, only 1 out of 6 was aneuploid. As PCNA staining, 2 of 6 in TCC G1 group and 5 of 6 in G3 group were positive. And it was noted examination was positive.

There have been no recurrence since transurethral resection in all IP in the study including the case recognized as aneuploid and positive for PCNA staining. But the present results suggest that among IPs, considered generally as a benign tumor, the case which has high proliferating character exists.