Malignant mesenchymoma

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. 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. 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. 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.