Biological characteristics of inverted papilloma of the urinary bladder

Objectives To elucidate the biological characteristics of inverted papilloma (IF) of the bladder. Materials and methods The immunoreactivity of p53, nuclear DNA content (assessed by ploidy and 2c deviation index [2cDI]) and the expression of proliferating cell nuclear antigen (PCNA) in 17 IPs were evaluated using a computer-assisted image analyser and compared with those in 12 superficial transitional cell carcinomas (TCCs), 29 invasive TCCs and one inverted papillary TCC of the bladder. Results Positive staining for p53 and PCNA and intense staining with Feulgen were observed predominantly in the basal layer of the bladder mucosa. All IPs and most superficial TCCs were diploid, while most invasive TCCs were aneuploid, Although the 2cDI and the immunoreactivities for PCNA and p53 were significantly lower in IPs than in invasive TCCs, there was no significant difference in these three variables between IPs and superficial TCCs. However, some IPs were more immunoreactive for p53 than were the superficial TCCs. Conclusions The distribution of cells with p53 and PCNA immunoreactivity, and with intense Feulgen staining, indicated that TP of the bladder might have high proliferative activity and that those IPs with a high immunoreactivity for p53 may be susceptible to malignant transformation.