Interphase cytogenetic analysis of myxoid soft tissue tumors by fluorescence in situ hybridization and DNA flow cytometry using paraffin- embedded tissue

Abstract

BACKGROUND. Myxoid liposarcoma is one of the major myxoid malignancies of soft tissue and its histologic differentiation from other myxoid tumors is sometimes difficult. Recent cytogenetic analysis revealed that a characteristic reciprocal chromosomal translocation of t(12;16)(q13;p11) occurs in myxoid liposarcomas. In this study, retrospective cytogenetic analysis by means of fluorescence in situ hybridization (FISH) and DNA flow cytometry were performed on free nuclei isolated from paraffin embedded myxoid liposarcoma cells, and they were compared with myxoid malignant fibrous histiocytomas (MFHs), low grade fibromyxoid sarcomas, and intramuscular myxomas. METHODS. Nine myxoid liposarcomas, five myxoid MFHs, two low grade fibromyxoid sarcomas, and four intramuscular myxomas were examined. Chromosomal aberrations in chromosomes 12 and 16 were investigated by FISH, using both centromeric DNA probes and whole chromosome painting probes. Cellular DNA contents were determined by flow cytometry. RESULTS. All nine myxoid liposarcomas were shown to be diploid by DNA flow cytometry and exhibited the translocation t(12;16), as shown by FISH. Four of the five myxoid MFHs exhibited aneuploidy, as shown by flow cytometry, and remarkable numeric aberrations of chromosomes 12 and 16. No abnormal DNA content or chromosomal aberrations were identified in the two low grade fibromyxoid sarcomas or the four intramuscular myxomas. CONCLUSIONS. FISH analysis performed on paraffin embedded materials can be used to differentiate myxoid liposarcomas from other myxoid soft tissue tumors.