SS18 and synovial sarcoma: DNA sequencing showed that the fusion sites of all SS18-SSX1 and the four classical SS18-SSX2 tumors were involved in exon 10 of the SS18 gene (codon 410) and exon 6 of the SSX1 or SSX2 genes (codon 111), which is typical of the ordinary fusion site of synovial sarcoma [23].