Cryptic chromosome rearrangement resulting in SYT-SSX2 fusion gene in a monophasic synovial sarcoma

Synovial sarcoma is cytogenetically characterized by the specific translocation t(X;18)(p11.2;q11.2), which results in the fusion of the SYT gene from chromosome 18 (18q11) with one of the genes from the X chromosome (Xp11) SSX1, SSX2, or SSX4. We present the case of a 51-year-old woman with a diagnosis of monophasic synovial sarcoma in which chromosome banding analysis did not reveal the presence of the typical t(X;18)(p11.2;q11.2), but instead found monosomy of chromosomes X and 18 and a marker chromosome. FISH analyses of the marker chromosome showed a rearrangement of the 5’ SYT region and the presence of pericentromeric sequences of chromosomes 18 and X. Comparative genomic hybridization detected losses of Xq21qter, 18p, and 18q12qter, indicating that the marker also contained DNA sequences from Xp22q21, and reverse-transcription polymerase chain reaction demonstrated a SYT-SSX2 fusion transcript. We uncovered a complex cryptic rearrangement that gives rise to the characteristic SYT-SSX2 fusion gene in a monophasic synovial sarcoma.