DISTINCT XP11.2 BREAKPOINT REGIONS IN SYNOVIAL SARCOMA REVEALED BY METAPHASE AND INTERPHASE FISH - RELATIONSHIP TO HISTOLOGIC SUBTYPES

Fluorescence in situ hybridization (FISH) and molecular analyses of sy novial sarcomas with cytogenetically similar (X;18)(p11.2;q11.2) trans locations have revealed two alternative breakpoint regions in Xp11.2, one residing in the ornithine aminotransferase-like 1 (OATL1) region a nd the other one in the related but distinct OATL2 region. As these re sults were obtained by different groups, we set out to evaluate an ext ended series of tumors with special emphasis on the two possible X-rel ated breakpoint regions. Together, seven synovial sarcomas were identi fied with a break in the OATL1 region and six with a break near OATL2, thereby confirming the actual existence of the two alternative Xp bre akpoint regions. We speculate that there seems to be a relationship be tween the occurrence of these breakpoint regions and the histologic ph enotype of the tumors, with a predominance of OATL1-related breakpoint s in the classical biphasic tumors and of OATL2-related breakpoints in the monophasic fibrous tumors.