Case of retroperitoneal dedifferentiated mixed-type liposarcoma: comparison of proliferative activity in specimens from four operations.

In a case of retroperitoneal dedifferentiated mixed-type liposarcoma, a dedifferentiated component was observed in the so-called mixed-type liposarcoma consisting of well-differentiated and myxoid components. The proliferative activity was compared among the different components of the tumor by immunohistochemical study using the proliferating cell nuclear antigen (PCNA) and MIB-1 monoclonal antibodies. The dedifferentiated component showed higher positivity than the well-differentiated and myxoid components, and tumor progression was most advanced in the dedifferentiated component. In the chronological examination of each component, the labeling indices of PCNA and MIB-1 were significantly higher at the third recurrence than in the primary lesion in all types, indicating that the proliferative activity of the tumor cells increased gradually. Considering the surgical treatment of liposarcoma, an extended resection encompassing normal adjacent tissues is required in cases containing the dedifferentiated component in comparison to the cases containing only well-differentiated or myxoid components. Copyright 1999 Wiley-Liss, Inc.