Detection of a variant SYT-SSX1 fusion in a case of predominantly epithelioid synovial sarcoma2

BACKGROUND: The translocation t(X;18)(p11.2;q11.2) characterizes synovial sarcoma, fusing the SYT gene at 18q11.2 to either SSX1 or SSX2 at Xp11.2. The usual chimeric product fuses SYT codon 379 to SSX1 or SSX2 codon 111. To date only three variant fusions have been identified. A predominantly epithelioid synovial sarcoma that expressed a novel variant of the SYT-SSX1 fusion is described. METHODS AND RESULTS: The current case was tested for the SYT-SSX fusion by reverse transcriptase polymerase chain reaction (PCR) followed by sequencing of the PCR product. Analysis revealed a 673 bp SYT-SSX1 chimeric product characterized by a novel junction of SYT codon 379 to SSX1 codon 83 with a 6 bp insertion at the fusion junction. CONCLUSION: As the number of reported variations of the SYT-SSX chimeric fusion increases in synovial sarcoma, the mechanics of the translocation machinery and the functional significance of these chimeric fusions will be better understood.