Micropapillary component of urothelial carcinoma detected in transurethral resection of bladder tumor (TUR-BT) tissues: a case report

A case of urothelial carcinoma (UC) containing a micropapillary carcinoma (MPC) component in the urinary bladder of an 83-year-old man is reported. The MPC component of UC has been reported to be a variant featuring poor prognosis and rapid progression. In the present case, a characteristic MPC component with micropapillary growth, in association with a fine meshwork-like stroma, was observed in less than 10% of fragmented cancer tissues of UC, G3, obtained by transurethral resection of a bladder tumor (TUR-BT). Lymphatic invasion was also detected. UC cancer cells had invaded the prostatic glands and replaced the original epithelial cells. The unique “insideout” feature of the MPC component was immunohistochemically obvious on staining with antibody to epithelial membrane antigen (EMA). On immunohistochemical study, cancer cells of both UC and MPC components were positive for pancytokeratin AE1/AE3 and cytokeratins 7 and 20. Carcinoembryonic antigen (CEA) and CAM5.2 were only focally positive in UC cells. MIB-1(Ki-67) labeling index was high, at 80%–90%, in cancer cells of UC. This was a case of UC, G3 with invasion to the muscularis propria layer of the urinary bladder and also to the prostate. MPC and MPC components in cancers should be recognized as a marker of poor prognosis, even when detected in less than 10% of UC within TUR-BT tissues, as in the present case.