RESUMO
We report a case of dedifferentiated liposarcoma of retroperitoneum as a recurrent form in a 41 year old male. The patient received a extirpation for retroperitoneal mass and diagnosed as myxoid liosarcoma 4 years ago. The patient experienced 3 recurrences over a period of 4 years and diagnosed as myxoid liposarcoma in the second, third recurrence also. Histologically, the mass was composed of several clearly distinct elements : well differentiated liposarcoma, myxoid liposarcoma, myxoid malignant fibrous histiocytoma, poorly differntiated sarcoma, and fibrosarcoma. Immunohistochemically, S-100 protein was expressed in the area of spindle cell sarcoma, well differentiated liposarcoma, and malignant fibrous histiocytoma but alpha-1-antichymotrypsin was only expressed in the area of myxoid malignant fibrous histiocytoma.