Adult ; Base Sequence ; DNA, Neoplasm ; genetics ; Exons ; Female ; Humans ; Liposarcoma ; genetics ; Liposarcoma, Myxoid ; genetics ; Male ; Middle Aged ; Molecular Sequence Data ; Oncogene Proteins, Fusion ; genetics ; Polymerase Chain Reaction ; methods ; RNA-Binding Protein EWS ; genetics ; RNA-Binding Protein FUS ; genetics ; Sequence Analysis, DNA ; Transcription Factor CHOP ; genetics ; Translocation, Genetic

Objective　The nature of myoid/myofibroblastic differentiation in dermatofibrosarcoma protuberans (DFSP) and its clinical and pathological significance were studied. Methods　124 DFSPs were reviewed by light microscopy. 6 cases with areas of myoid/myofibroblastic differentiation were assayed with immunohisto-chemical technique and electron microscopy was applied in two cases. Results　Myoid/myofibroblastic differentiation occurred most commonly in fibrosarcomatous DFSP (FS-DFSP). It was recognized histologically as peripherally distributed or randomly scattered small eosinophilic nodules or short bundles, which were composed of bland spindle cells, closely resembling smooth muscle cells or myofibroblasts. Immunohistochemically, cells in myoid/myofibroblastic areas showed positive staining for α-SMA, MSA and vimentin, but negative for desmin and CD34. Electron microscopic study displayed the presence of microfilament bundles, focal dense bodies and micropinocytic vesicles, consistent with those of myofibroblasts. Conclusion　Myoid/myofibroblastic areas in DFSP possibly represents the hyperplasia of stromal myofibroblasts, rather than true myofibroblastic differentiation of the neoplastic cells.

OBJECTIVETo assess the feasibility of detecting SYT-SSX fusion transcripts in paraffin-embedded tissues of synovial sarcoma by reverse transcription-polymerase chain reaction (RT-PCR).

METHODSRT-PCR was used to amplify the SYT-SSX fusion transcripts using archival formalin-fixed paraffin-embedded tumor specimens from a series of 37 synovial sarcoma cases. To investigate the specificity of the SYT-SSX fusion transcripts, a variety of non-synovial sarcoma tumors were included in the study as negative controls. The detected messages derived from fusion genes were confirmed by subsequent sequence analysis.

RESULTSSYT-SSX fusion transcripts were detected in 33 of 37 (89.2%) synovial sarcomas. None of the 34 cases of non-synovial sarcoma tumors showed amplified products of SYT-SSX fusion transcripts, although PBGD mRNA was detected in all specimens. Among 33 SYT-SSX-positive synovial sarcomas, 22 tumors had an SYT-SSX 1 fusion transcript, whereas 6 tumors had an SYT-SSX2 fusion transcript. Fusion types can not be distinguished in the remaining 5 cases. There was a significant relationship between SYT-SSX fusion type and histologic subtype. All 10 biphasic synovial sarcomas had the SYT-SSX1 fusion, whereas all tumors with SYT-SSX2 were of monophasic morphology (P < 0.05).

CONCLUSIONSRT-PCR can be applied to archival formalin-fixed paraffin-embedded tumor tissues as a sensitive and reliable technique for the diagnosis and differential diagnosis of synovial sarcoma. There is an association between SYT-SSX fusion type and histological subtype. SYT-SSX2 fusion transcripts can only be found in monophasic synovial sarcoma.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Female ; Humans ; Male ; Middle Aged ; Oncogene Proteins, Fusion ; genetics ; Paraffin Embedding ; RNA, Messenger ; analysis ; Reverse Transcriptase Polymerase Chain Reaction ; Sarcoma, Synovial ; genetics ; pathology