Myxoid liposarcoma with t (12; 16)(q 13; p 11). Possible usefulness of chromosome analysis in a poorly differentiated sarcoma

A chromosomal study was used to establish diagnosis of a poorly differentiated soft-tissue sarcoma occurring in the right thigh of a 57-year-old Japanese female. Histopathologically the excised tumor consisted of a poorly differentiated myxoid neoplasm, without specific features to enable the identification of neoplastic cells. Although a tentative diagnosis of poorly differentiated myxoid liposarcoma was made, ultrastructural examination and Oil Red O fat stain failed to demonstrate the evidence of lipoblastic differentiation, except that occasional cells possessed a small number of fine fat droplets. The diagnosis of liposarcoma was suggested by chromosome analysis of the fresh tumor tissue after short time culture and trypsin-Giemsa banding technique. The tumor cells demonstrated a clonal abnormality characterized by a reciprocal translocation, t(12; 16)(q 13; p 11), which is known as a specific aberration in myxoid liposarcoma. Thus, chromosome study seems to be useful for identifying undifferentiated mesenchymal tumors, which lack morphologic evidence of any specific differentiation, as in the present case.