[The inverted papilloma of the urinary bladder (author's transl)].

Regarding the characteristics of the inverted papilloma of the urinary bladder a report is given on two of our own observations, and its histogenesis is discussed. Out of 41 reported cases 21 patients developed symptoms of bladder obstruction and 15 patients had macrohaematuria. With exception of two cases, all the tumors were localized in the bladder neck, they were mostly solitary and in some cases pedunculated. Microscopically they showed papillomatous structures growing inverted into the stroma with only little signs of proliferation as well as microcysts with PAS-positive material, and always they had distinct borders between epithelium and connective tissues. In 33 out of 41 cases control cytoscopy was performed between 6 months and 17 years after resection. Only one case showed recidivation of the tumor.