Inverted Papilloma of the Urinary Bladder: 3 Cases

Huh, Jung Sik; Kim, Duk Kyo; Lee, Choong Hyun; Kim, Jin Il

Abstract

Inverted papilloma of the urinary bladder is a rare urothelial neoplasm, almost benign in its histologic morphology and clinical behavior. It occurs mainly in males and in the region of the trigone of bladder, or posterior urethra. But, it may arise in the renal pelvis. The characteristic downward proliferation of urothelial cells within the underlying lamina propria is of such magnitude as to an exophytic papillomatous tumor. The lesion may be easily mistaken for a low- grade papillary transitional cell carcinoma, although the histologic appearance is distinctly different, as is its subsequent behavior. Because of distinctive histologic features and patterns of growth it is possible to differentiate between two basic types of inverted papillomatous which were termed "trabecular" and "glandular". The trabecular type consists of widely branched, anastomosing cords of urothelial cells originating directly from the overlying transitional epithelium. The glandular type develops apparently from a proliferative cystitis cystica and glandularis which, therefore, should be considered a potentially preneoplastic lesion. The malignant tendency is now being reported with inverted papillomas of urinary tract and therefore they are no longer regarded as innocuous benign neoplasms. We report the 3 cases of inverted papilloma of the urinary bladder with a brief review of literature.