USE OF FISH TO DETECT CHROMOSOMAL TRANSLOCATIONS AND DELETIONS - ANALYSIS OF CHROMOSOME REARRANGEMENT IN SYNOVIAL SARCOMA-CELLS FROM PARAFFIN-EMBEDDED SPECIMENS

Retrospective cytogenetic analysis was performed on paraffin-embedded cells from five cases of synovial sarcoma to evaluate the frequency of the X;18 translocation characteristic of this tumor. Fluorescent in s itu hybridization with DNA probes for the centromeres of chromosomes X and 18 was used with whole chromosome painting probes for X and 18. T ranslocation was inferred when there were only two X and 18 centromere signals but three painting probe signals of unequal size. On this bas is it was possible to identify the t(X;18) in three cases. The fourth case was found to have extra copies of chromosome 18 without transloca tion, while the fifth case, the only one with a questionable diagnosis , had a normal chromosome pattern with a minor clone showing a translo cated 18 but a normal X. Thus this study demonstrates the feasibility and value of using fluorescent in situ hybridization to detect chromos ome rearrangements in archival tumor specimens.