[Inverted transitional-cell papilloma: the expression of the Ki-67 nuclear antigen as a prognostic factor]

This study attempted to correlate the clinical course and outcome of transitional cell inverted papilloma and the number of active cell nuclei, using Ki-67 antigen expression to quantify nuclear activity.

We analyzed thirteen pathologically confirmed lesions of transitional epithelial inverted papilloma in 12 patients that had been treated from 1977-1994. Immunohistochemical labelling of the tumor was performed using Mib-1 antibodies (a marker for the Ki-67 cell proliferation-associated cyclin) that identify active cell nuclei. Then we counted the number of active nuclei per 10 fields at high magnification (400x).

The tumor was localized to the bladder in 11 cases and one case had 3 concomitant lesions in the renal pelvis. Five cases were associated with low grade urothelial transitional cell carcinoma, which was concomitant in one and asynchronous in the remaining 4 cases. One patient with inverted papilloma recurred and subsequently developed low grade transitional cell carcinoma. The elevated number of nuclei in the proliferative phase (more than 100 active nuclei per 10 high power fields) did not show a consistent correlation with good outcome.

Treatment of inverted papilloma should be as in superficial transitional cell papillary carcinoma, since this tumor type may recur or be associated with transitional cell carcinoma. The lesions with a high proliferative activity, which is easily determined by Ki-67 antigen quantification, generally have a poor outcome.