DUAL-COLOR FLUORESCENCE IN-SITU HYBRIDIZATION ANALYSIS OF SYNOVIAL SARCOMA

Mounting cytogenetic evidence indicates that synovial sarcomas, regard less of histological conformation, share the specific reciprocal chrom osomal translocation t(X;18)(p11.2;q11.2). Application of dual-colour fluorescence in situ hybridization (FISH) on interphase nuclei isolate d from archival paraffin-embedded material to identify the specific tr anslocation is of diagnostic importance for pathological practice and retrospective study. Five cases of well-characterized biphasic synovia l sarcomas, two monophasic fibrous synovial sarcomas, one embryonal rh abdomyosarcoma, one fibrosarcoma, and one malignant peripheral nerve s heath tumour were analysed. To visualize the translocated chromosomal fragments and their topographic relationships with centromeres of chro mosomes X and 18, nuclei from each case were hybridized concurrently w ith chromosome X centromeric and chromosome 18 painting probes, and ch romosome 18 centromeric and chromosome X painting probes, respectively . Six out of seven synovial sarcomas showed chromosomal alterations co nsistent with t(X;18). One biphasic synovial sarcoma had trisomy 18 an d lacked the chromosomal translocation t(X;18). The other three spindl e cell sarcomas and the normal control tissues showed the normal numer ical and structural composition for chromosomes X and 18. It is indica ted from the present study that when histological differential diagnos is is difficult, FISH would be a crucial aid in detecting a known spec ific chromosomal alteration and that dual-colour FISH is an efficient stable diagnostic tool for pathological research and daily diagnosis. The results also suggest that rare synovial sarcomas may lack the chro mosomal translocation t(X;18). (C) 1998 John Wiley & Sons, Ltd.