Pleomorphic liposarcoma: a clinicopathological, immunohistochemical and molecular cytogenetic study of 32 additional cases.

The purpose of this study is to report the author's experience with 32 cases of pleomorphic liposarcoma to further broaden the clinicopathological spectrum. The tumours occurred equally in males and females with ages ranging from 11 to 83 years (median, 56 years). Tumour site included the extremities (17 cases), abdomen/retroperitoneum (4 cases), internal organs (5 cases), thoracic cavity/mediastinum (2 cases), orbit, neck, groin and scrotum (1 case each). The diagnostic pleomorphic lipoblasts were identified in 31 primary tumours and one recurrent tumor but varied widely in proportion between cases or different areas of the same tumor. Four tumors contained sheets or focal aggregates of lipoblasts with epithelioid morphology. The nonlipogenic component in 26 cases had an appearance of undifferentiated pleomorphic sarcoma, whereas in six cases it was consistent with intermediate to high grade myxofibrosarcoma. The pleormorphic and epithelioid lipoblasts displayed variable expression of S100 protein. There was no signal of amplified MDM2 gene in 10 cases tested by fluorescence in situ hybridization. This study further illustrates that pleomorphic liposarcoma is a distinctive entity with no relationship to either well differentiated liposarcoma or dedifferentiated liposarcoma. Albeit very rare, pleomorphic liposarcoma can occur in teenaged patients and internal organs.