Masked t(X;18)(p11;q11) in a biphasic synovial sarcoma revealed by FISH and RT-PCR.

The initial cytogenetic analysis of a biphasic synovial sarcoma showed an apparently normal karyotype. After FISH using chromosome X- and 18-specific probes and RT-PCR using SYT- and SSX-specific primer sets, a cryptic synovial sarcoma-associated t(X;18)(p11;q11) could be revealed. The "masked" nature of the translocation may best be explained by a two-step scenario in which a genuine t(X;18)(p11;q11) has occurred as a first step and a reverse reciprocal X;18 translocation as a second step, leaving the synovial sarcoma-associated SYT-SSX1 fusion intact. The findings further underline our previous suggestion that SYT-SSX1 fusions may correlate with a biphasic nature of the tumor. In addition, our findings indicate that, in analogy to, e.g., the Philadelphia translocation in chronic myeloid leukemia, "masked" translocations may occur in soft tissue tumors and that, as a standard, RT-PCR and/or FISH analyses should be carried out in order to provide karyotypic information that may be relevant to tumor diagnosis and/or prognosis.