[Inverted papilloma of the bladder]

No more than 40 cases of inverted papilloma (IP) of the urinary bladder have been reported in literature. The author presents 2 observations of IP in both of which the epithelial transitional cellular structures showed submerged pseudoinvasive growth and a peculiar inversion of the villous strucure. The tumor is benign clinically and histologically, its benign nature is confirmed by the remote results of observations. Despite the fact that the histogenesis of IP is not quite clear yet, the author, as most other investigators, classify IP according to the International Histological Classification as benign tumor differing from common papillomas of the urinary bladded only in the direction of the growth and the arrangement of villous structures.