Malignant mesenchymoma of the small intestine.

We present the clinical and pathologic features of a malignant mesenchymoma of the small intestine. Light and electron microscopic studies of the sarcoma revealed multiple patterns of differentiation, including fibrosarcoma, leiomyosarcoma, chondrosarcoma, and osteosarcoma. A recurrence had the morphologic nature of a mesenchymal chondrosarcoma. Clinically, the neoplasm was not detected by barium contrast radiography, but it was readily defined by sonography and computed tomography. Despite aggressive surgery and chemotherapy, the patient died 15 months after the diagnosis was made.