[Dedifferentiated liposarcoma. A clinico-pathologic study of 6 cases].

During a period of 15 years, 6 cases of dedifferentiated liposarcomas were found among 542 cases of adult soft tissue sarcomas, 77 of which were liposarcomas. They were huge tumors of the retroperitoneum, containing distinct areas of well-differentiated liposarcoma most often of sclerosing type and malignant fibrous histiocytoma or undifferentiated sarcoma most often of high grade malignancy. Immunohistochemistry on the dedifferentiated component showed a positivity with anti-vimentin and alpha-1-antichymotrypsin in 5 cases and with anti-alpha smooth muscular actin in 4 cases. Three patients developed local recurrence and a fourth one quickly died with bone metastasis. Other types of dedifferentiated sarcomas, the process of dedifferentiation and links between malignant fibrous histiocytoma and dedifferentiated sarcomas are discussed.