The epithelial origin of a malignant mesodermal mixed tumor of the bladder: report of a case with long-term survival.

Malignant mesodermal mixed tumors of the bladder are complex neoplasms consisting of elements of carcinoma and differentiated sarcoma. They are rare, aggressive and usually rapidly fatal. We report on a patient who remained free of disease 7 years after resection by partial cystectomy of a malignant mesodermal mixed tumor. Only 1 other long-term survivor has been reported. Our case is of particular interest because urothelial carcinoma in situ was found in the bladder epithelium on the surface and at the periphery of the invasive tumor, strongly suggesting an epithelial origin of this and similar tumors of other organs.