Variation in myxoid liposarcoma: Clinicopathological examination of four cases with detectable TLS-CHOP or EWS-CHOP fusion transcripts whose histopathological diagnosis was other than myxoid liposarcoma.

Liposarcomas are separated into clinicopathological entities by a characteristic morphological spectrum and distinctive genetic changes. Myxoid liposarcoma (MLS) represents one such entity with specific chromosomal translocations leading to the generation of fusion genes, the human translocation liposarcoma (TLS)-CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) or the Ewing sarcoma (EWS)-CHOP. In the present study, four cases of liposarcoma with detection of TLS-CHOP or EWS-CHOP, whose postoperative diagnosis was other than MLS (one well-differentiated liposarcoma, two de-differentiated liposarcomas and one unclassified) were examined for medical records, imaging data and histopathology. Clinical records demonstrated that three of the four cases were considerably difficult to diagnose definitively, and histopathological re-examination pointed out areas of myxomatous change as a minor component (<10%). Their dominant components (>90%) resembled pleomorphic sarcoma, pleomorphic malignant fibrous histiocytoma and monophasic synovial sarcoma. The current cases may represent an extreme variant of the morphological spectrum within MLS. In cases of difficulty in making definitive diagnosis of soft tissue sarcoma by standard histopathological examination and identification of myxoid stroma even as a minor component, analyzing TLS-CHOP and EWS-CHOP fusion genes may aid the diagnosis of unusual MLS.