A Study Of The Synovial Sarcoma On Histopathology, Immunohistochemistry And Molocular Biology

Objectives: Synovial sarcoma is a malignant soft tissue tumors of uncertain type. It has variable changes of microscopic features. Therefore, it is difficult for us to make a diagnosis of synovial sarcoma in clinical practice. Especially for monophasic type and poorly differentiated (round cell) type, we must be carefully distinguish them from malignant peripheral nerve sheath tumor (MPNST), flbrosarcoma, leiomyosarcoma, Ewing's sarcoma, malignant lymphoma and so on. Our study based on clinical practice, and researched the synovial sarcoma from three aspects: histopathology, immunochemistry, and molecular biology. Our aim is to provide some scientific basis for clinical diagnosis, differential diagnosis, and judgment of prognosis.Materials and Methods: 41 synovial sarcoma cases were collected. All cases were observed under microscope; 36 cases were signed by SP methods, and antibodies were respectively CK, EMA, Vim, SMA, Des, s-100, PCNA, PGP; 20 cases were selected for reverse transcription-polymerase chain reaction (RT-PCR) methods to detect fusion gene SYT-SSX, which was induced by balance translocationResults:(1) In all 41 synovial sarcoma cases, monophasic fibrous type was 22 (53.7%); biphasic type was 11 (26.8%); monophasic epithelial type was 1 (2.4%); poorly differentiated (round cell) type was 7 (17.1%). Mast cells were observed in 8 (19.5%) cases.(2) CK positive cases were 27 (75.0%) in the epithelial cell component; EMA positive cases were 30 (83.3%) also in the epithelial cell component; Vim positive cases were 35 (97.2%) in the spindle cell component; Des positive cases were 4 (11.1%); s-100 positive cases were 1 (2.8%); PGP positive cases were 26 (72.2%); PCNA positive cases were 33 (91.7%). Des and s-100 were both focal positive reaction. CK or EMA (including CK and EMA both) positive, meanwhile Vim positive cases were 31 (86.1%); CK and EMA negative, Vim positive cases were 4 (11.1%); CK and EMA negative, Vim also negative cases were 1 (2.8%). SMA were all negative cases.(3) House-keeping gene PBGD mRNA can be detected in every test . SYT-SSX fusion transcript was detected in 18 tumor cases (90%). In 18 SYT-SSX positive SS cases, 12 present SYT-SSX1 fusion transcript and 6 present SYT-SSX2 fusion transcript. SYT-SSX1 fusion transcript can be seen in 9 monophasic SS and 3 biphasic SS. In 6 SYT-SSX2 positive SS cases, 4 were monophasic SS and 2 were biphasic.Conclusion:1 Diagnosis of synovial sarcoma relied on 4 aspects:(1) The patient was adult, and the tumor occurs near large joints of extremities.(2) Biphasic differentiate clues (such as epithelial cells, gland-like structure) were observed under microscope. Appearance of mast cells supported the diagnosis.( 3 ) By immunochemistry staining, both epithelium marker and mesenchyme marker were positive, which made further support for diagnosis.(4) Fusion gene SYT-SSX induced by translocation was detected by RT-PCR methods.2 Diagnosis basis, as mentioned above, all can be regarded as differential diagnosis basis: MPNST, fibrosarcoma, leiomyosarcoma, Ewing's sarcoma, malignant lymphoma and so on.3 The detection of SYT-SSX fusion transcripts in FFPE tissues by RT-PCR method for diagnosis of SS is feasible and sensitive. It is also valuable for clinical diagnosis, differential diagnosis and judgment of prognosis.