BACKGROUND: Malignant mesenchymomas are rare soft tissue tumors that contain two or more distinct histologic subtypes of sarcoma within the same tumor (exclusive of a fibrosarcomatous or hemangiopericytomatous component). They are generally considered high grade neoplasms and are associated with a poor prognosis, although experience with these tumors is limited. METHODS: We report 8 patients seen at our center over the last 22 years and describe the clinical course of a patient with a malignant mesenchymoma arising in the retroperitoneum whose experience typifies the aggressive behavior of this tumor. RESULTS: All eight patients had large, high grade tumors located in the retroperitoneum or thigh. Six of the 8 died of disease and 2 were alive with disease at a median of 30 months from diagnosis. CONCLUSIONS: Malignant mesenchymoma represents a particularly aggressive form of soft tissue sarcoma. Our experience with this disease highlights the need for more effective treatment strategies for these patients.
