The biphasic subtype of synovial sarcoma consists of both epithelial and spindle cell components. To address the relationship between the different cellular components found in synovial sarcoma, we deduced the presence of the synovial sarcoma-specific der(X)t(X;18)(p11.2;q11.2), and involvement of the SSX1 gene in both the epithelial/glandular and spindle cell components of 3 biphasic synovial sarcomas with wide ranging proportions of each of the 2 elements. This has been achieved using a 2-color fluorescence in situ hybridization (FISH) methodology that we had developed recently for analysis paraffin-embedded material. The presence of the rearrangement could be deduced in histologically defined regions and the results showed clearly that the rearrangement was present in both cellular components. This finding provides direct genetic evidence for biphasic synovial sarcomas being clonal and truly biphasic.
Copyright 1999 Wiley-Liss, Inc.