Cryptic t(X;18), ins(6;18), and SYT-SSX2 gene fusion in a case of intraneural monophasic synovial sarcoma

V.S. Lestou, J.X. O'Connell, M. Robichaud, C. Salski, J. Mathers, J. Maguire, I. Chudoba, P.H.B. Sorensen, W. Lam, D.E. Horsman

A 54-year-old male presented with a spontaneous peroneal nerve palsy and a diagnosis of monophasic synovial sarcoma (SS) was rendered by histologic examination. Cytogenetic analysis revealed a complex abnormal karyotype without evidence of the typical t(X;18)(p11;q11) associated with SS. Subsequent reverse transcriptase polymerase chain reaction analysis showed the presence of an SYT/SSX2 fusion transcript, confirming the presence of a cyptic t(X;18). In light of -X, -18 and marker chromosomes evident in the G-band karyotype, it was suspected that a cryptic chromosomal rearrangement involving the marker chromosomes would harbor an X;18 fusion. Multi-colored karytotyping (M-FISH) revealed a previously unrecognized t(X;18) and t(5;19) in the marker chromosomes as well as unrecognized ins(6;18) and t(16;20). The addition of M-FISH analysis in this case led to the identification of complex inter-chromosomal rearrangements, thus providing an accurate karyotype.