Carcinosarcoma of urinary bladder: report of 5 cases with immunohistologic study.

We studied 5 cases of carcinosarcoma of the urinary bladder. Immunoperoxidase studies were performed to identify the nature of the tumor and to establish the diagnosis. We suggest that these tumors represent a transition of epithelial to mesenchymal malignancy. Three of our patients had a history of radiation therapy prior to development of carcinosarcoma; of which 2 had a long interval between exposure to radiation and tumor development. Radiation is a risk factor for endometrial carcinosarcoma, and in this report we strongly suggest such an association for the urinary bladder.