Malignant hemangiopericytoma and other sarcomas with hemangiopericytoma-like pattern.

This clinicopathologic study concerns 19 cases of malignant hemangiopericytoma among 755 cases of soft tissue sarcomas. The age of the patients ranged from 18 to 76 years, with a median of 43 years. Tumors occurred on the trunk in 8, lower extremities in 5, the head in 3, and the retroperitoneum in 3. According to follow-up information, nine of the 19 patients had died. Histologically the tumor was characterized by its homogeneous vascular pattern, its uniform cell population and a wide range of cellular anaplasia. After extensive sampling of the tumors, a comparative light microscopy revealed differences in diagnostic histology between malignant hemangiopericytoma and other soft tissue sarcomas with a hemangiopericytoma-like vascular pattern. The frequency of appearance of such pericytoma pattern in different soft tissue sarcomas was as follows: 4/4 cases (100%) in extraskeletal mesenchymal chondrosarcoma, 11/14 (79%) in infantile fibrosarcoma, 27/45 (60%) in synovial sarcoma, 62/201 (30%) in malignant fibrous histiocytoma, 9/37 (25%) in malignant schwannoma and 6/72 (8%) in liposarcoma.