[Demonstration of SYT-SSX11/2 fusion transcripts in synovial sarcomas using RT-PCR]

Various mesenchymal malignancies with a spindle cell morphology may mimic monophasic synovial sarcomas. We analysed, whether detection of SYT-SSX1/2 fusion transcripts, present as a consequence of a specific translocation [t(X;18)(p11.2;q11.2)] found in synovial sarcomas, are useful to confirm the diagnosis of synovial sarcoma. A nested RT-PCR protocol was established for the detection of SYT-SSX1/2 fusion transcripts. After RNA extraction of snap frozen tissue reverse transcription was carried out. In a nested PCR, the resulting cDNA samples were amplified and visualized on agarose gels. DNA sequencing of PCR products enabled the assignment of fusion transcripts to either the SYT-SSX1 or the SYT-SSX2 variant. We detected SYT-SSX1/2 fusion transcripts in seven monophasic and three biphasic synovial sarcomas. 20 out of 21 control tumour including leiomyosarcomas, malignant peripheral nerve sheath tumours, gastrointestinal stromal sarcomas and fibrosarcomas were negative in RT-PCR analysis. One case of recurrent spindle cell sarcoma originally classified as a fibrosarcoma revealed a SYT-SSX2 fusion transcript. These data provide further evidence that the RT-PCR amplification of SYT-SSX1/2 fusion transcripts permits the specific identification of synovial sarcomas. This diagnostic approach may be especially useful in cases with equivocal histomorphology.