A reverse transcriptase-polymerase chain reaction assay in the diagnosis of soft tissue sarcomas

BACKGROUND. Many types of sarcomas are characterized by specific chromosoma l translocations that result in the production of novel chimeric genes. Det ection of these fusion genes could be a sensitive molecular diagnostic assa y. However, to the authors' knowledge there have been few systemic comparis ons between the current histopathologic diagnosis and the presence or absen ce of particular fusion genes in patients with adult soft tissue sarcomas ( STSs). METHODS. Total RNA was extracted from 75 cases of STS and analyzed by rever se transcriptase-polymerase chain reaction (RT-PCR) assay for the detection of a variety of fusion transcripts. The results of the molecular assay wer e compared with standard histopathologic diagnoses. RESULTS. Of the 18 tumors diagnosed as synovial sarcoma, 17 (94%) expressed SYT-SSX chimeric transcripts. AU nine myxoid liposarcomas were positive fo r FUS-CHOP fusion transcripts. Of the four cases of Ewing sarcoma, two had an EWS-FLI1 fusion transcript and one had an EWS-ERG fusion transcript. A c lear cell sarcoma had a EWS-ATF1 fusion transcript. None of 19 cases of mal ignant fibrous histiocytoma nor 3 leiomposarcomas contained a fusion transc ript. Three cases with an initial diagnosis other than synovial sarcoma exp ressed a SYT-SSX fusion transcript. A review of the slides and additional e xamination showed that a diagnosis of synovial sarcoma was appropriate for these cases. There was a trend for biphasic synovial sarcoma to contain the SYT-SSX1 fusion. CONCLUSIONS, The authors believe RT-PCR assay for the detection of a specif ic fusion gene provides a useful tool for confirmation of the diagnosis of adult STS in diagnostically difficult cases and in retrospective studies. ( C) 2000 American Cancer Society.