Mixed micropapillary and trophoblastic carcinoma of bladder: report of a first case with new immunohistochemical evidence of urothelial origin.

The micropapillary variant of urothelial carcinoma has a reported incidence of 0.7%. Trophoblastic urinary carcinoma is very rare, with roughly 30 cases reported during the last century. This is the first report of mixed micropapillary and trophoblastic bladder carcinoma. A 45-year-old man presented with gross hematuria. His tumor contained choriocarcinomatoid areas with syncytiotrophoblasts, classic micropapillary carcinoma, conventional high-grade urothelial carcinoma, and flat carcinoma in situ. He underwent radical surgery; tumor stage was T4N2M0. Despite postoperative combination chemotherapy, he developed pulmonary and retroperitoneal metastases and died 20 months after presentation. The tumor was immunopositive for human chorionic gonadotropin and human placental lactogen in trophoblast and for cytokeratin 20 and high-molecular-weight cytokeratin in all tumor components. Because high-molecular-weight cytokeratin is expressed by urothelium but is rarely found in placental trophoblast or germ-cell choriocarcinoma, its presence in trophoblastic bladder carcinoma is new evidence that the latter is a transformed neoplasm of urothelial origin.