Clinical impact of molecular and cytogenetic findings in synovial sarcoma

Synovial sarcoma is an aggressive soft-tissue tumor that accounts for up to 10% of soft-tissue sarcomas. Cytogenetically, synovial sarcoma is characte rized by the t(X; 18)(p11 ;q11), found in more than 95% of the tumors. This translocation results in rearrangements of the SYT gene in 18q11 and one o f the SSX1, SSX2, or SSX4 genes in Xp11, creating a SYT/SSX1, SYT/SSX2, or SYT/SSX4 chimeric gene. It has been shown that patients with SYT/SSX1 fusio n genes have a shorter metastasis-free survival than do patients with SYT/S SX2. Previous studies have also suggested that clonal evolution may be asso ciated with disease progression. In the present study, RT-PCR analysis show ed that all 64 examined synovial sarcomas from 54 patients had SYT-SSX chim eric genes. SYT/SSX1 was found in 40 tumors from 33 patients, SYT/SSX2 in 2 3 tumors from 20 patients, and SYT/SSX4 in one case. Two patients had varia nt SYT/SSX2 transcripts, with 57 bp and 141 bp inserts, respectively, betwe en the known SYT and SSX2 sequences. Patients with tumors with SYT/SSX1 fus ions had a higher risk of developing metastases compared to those with SM/S SX2 fusions (P = 0.01). The reciprocal transcripts SSX1/SYT and SSX2/SYT we re detected using nested PCR in I I of the 40 samples with SYT/SSX1 and 5 o f the 23 samples with SYT/SSX2, respectively. Among 20 blood samples, SYT/S SX1 and SYT/SSX2 were detected in one sample each. The t(X;18), or variants thereof, was found cytogenetically in all patients but three. Among 32 pri mary tumors, the t(X; 18) or a variant translocation was the sole anomaly i n 10. In contrast, of the seven metastatic lesions that were investigated p rior to radiotherapy, only one had a t(X;18) as the sole anomaly; all other tumors displayed complex karyotypes. Cytogenetic complexity in primary tum ors was, however, not associated with the development of metastases. Tumors with SYT/SSX2 less often (4/12 vs. 7/15) showed complex karyotypes than di d tumors with SYT/SSX1, but the difference was not significant, Combining c ytogenetic complexity and transcript data, we found that the subgroup of pa tients with tumors showing simple karyotypes and SYT/SSX2 fusion had the be st clinical outcome (2/8 patients developed metastases), and those with tum ors showing complex karyotypes together with SYT/SSX1 fusion the worst (6/7 patients developed metastases). This corresponded to 5-year metastasis-fre e survival rates of 0.58 and 0.0, respectively (P = 0.02). (C) 2001 Wiley-L iss, Inc.