LIPOSARCOMA - STUDY OF 55 CASES WITH A REASSESSMENT OF ITS CLASSIFICATION

Fifty-five cases of liposarcoma were reviewed. The cases were classified on the basis of histopathologic findings as follows: myxoid, 29 cases; well-differentiated, 11 cases; dedifferentiated, eight cases; pleomorphic, four cases; combined well-differentiated and pleomorphic, two cases; and unclassified, one case. The term 'dedifferentiated liposarcoma' is proposed for tumors containing distinct areas of well-differentiated liposarcoma and cellular nonlipogenic spindle-cell or pleomorphic sarcoma. All patients except one were adults. Myxoid and pleomorphic liposarcoma predominantly involved the thigh, while well-differentiated, dedifferentiated, and combined well-differentiated-pleomorphic liposarcoma showed a marked preference for the retroperitoneum. The survival of patients with pleomorphic and dedifferentiated liposarcoma was significantly poorer than that of those with the myxoid and well-differentiated varieties. There was a marked tendency toward local recurrence in all types. Recurrent myxoid and pleomorphic liposarcomas were often controlled by additional therapy, whereas recurrences of other types usually were not; this difference was considered largely a result of locational factors. Metastasis was observed in 10 cases of myxoid liposarcoma, three of pleomorphic liposarcoma, and two of dedifferentiated liposarcoma. In myxoid liposarcoma, initial treatment consisting of excision followed by radiation resulted in a significantly reduced rate of local recurrence as compared with excision alone, and more extensive hypercellular zones were associated with increased metastatic potential. 'Round cell' liposarcoma was not found to be an independent type; all cases for which this designation might have been considered could be better classified as myxoid liposarcoma with cellular areas (usually) or pleomorphic liposarcoma with rounded cells (rarely). The resemblance of portions of some dedifferentiated and pleomorphic liposarcomas to 'malignant fibrous histiocytoma' was sufficient to deny the specificity of the histologic pattern of the latter.