Cytogenetic and immunohistochemical profile of myxoid liposarcoma

Cytogenetic and immunohistochemical studies were performed in nine myxoid liposarcomas. The tumor karyotype was determined after short-term culture of cells in vitro. Immunohistochemical studies were performed on frozen tissue in five cases and on paraffin-embedded tissue in three cases. Chromosomal analysis demonstrated a balanced translocation t(12;16) (q13;p11) as the sole abnormality in four cases. Two cases showed an association with other abnormalities. Three tumors showed variants of the t(12;16) translocation involving other chromosomes. In all cases studied, the 12q13 breakpoint was involved in rearrangements. In the majority of cases, immunohistochemical studies demonstrated vimentin (9 of 9) and S-100 protein (8 of 9). Strong focal expression of desmin was observed in two tumors. Weak focal expression was observed in three tumors. Two tumors, which were both desmin positive, showed focal expression of MSA and alpha-SMA. Strong expression of CD36 was present in all four cases that were studied for this marker. CD34 was negative in tumor cells, but it highlighted an intricate capillary network in the tumor. Close relationship between the tumor cells and pericapillary pericytes was demonstrated with CD34 and alpha-SMA strains. The authors conclude that myxoid liposarcoma is characterized by a specific chromosomal rearrangement. Its immunohistochemical profile is wider than previously believed, including expression of muscle markers.