Inverted Variant of Urothelial Carcinoma of the Urinary Bladder : A Case Report

A 69-year-old male complained of gross hematuria. Cystoscopy revealed a papillary pedunculated tumor. The tumor was approximately 4 cm in length, and mimicked an inverted papilloma with a small stalk and smooth surface, located on the bladder trigone. Transurethral resection of the bladder tumor was performed, and the tumor was resected en bloc. Histopathological examination revealed thick and irregular epithelial cords. Immunohistochemically, Ki-67 labeling index was 5%, p40 and CK7 were positive, and CK20 was negative. Then, this tumor was diagnosed as inverted variant of urothelial carcinoma. Even when gross appearance is compatible with inverted papilloma, pathological and immunohistochemical examinations are essential for accurate diagnosis of inverted bladder tumor. No recurrence was observed by cystoscopy 13 months after the resection.