DETECTION OF THE SYT-SSX CHIMERIC RNA OF SYNOVIAL SARCOMA IN PARAFFIN-EMBEDDED TISSUE AND ITS APPLICATION IN PROBLEMATIC CASES

We report the development of a reverse-transcriptase polymerase chain reaction assay that detects (in paraffin-embedded, formalin-fixed tiss ue) the SYT-SSXchimeric RNA transcript resulting from the t(X;18) of s ynovial sarcoma. The primers chosen detect both of the SSX1 and SSX2 p artners, and the target sequence is small enough (87 base pairs) to be reliably detected in archival and variably processed consultation mat erial. To demonstrate its usefulness, we applied it to 14 problematic cases, including spindle cell tumors of the thoracic region, of the ne ck, and of subcutaneous tissue, For instance, we show that, depending on the location, synovial sarcoma can mimic malignant solitary fibrous tumor, the spindle epithelial tumor with thymus-like differentiation, or skin adnexal tumors, Molecular detection of the SYT-SSX chimeric R NA should allow the reclassification of difficult cases in which the m orphologic features overlap different entities or in which tumor nosol ogy is still evolving.