Carcinosarcoma of the colon: a rare cause of colovesical fistula.

Carcinosarcomas are relatively rare tumors composed of both carcinomatous and sarcomatous components. The most common sites involved by this tumor are the head and neck, respiratory tract, uterus, ovaries, and fallopian tubes. Within the gastrointestinal tract this tumor most often occurs in the esophagus, followed by the stomach. Carcinosarcomas are very aggressive tumors associated with a poor prognosis. The first case of carcinosarcoma of the colon was reported in 1986. The case reported here is the only one involving an associated colovesical fistula.