OBJECTIVE To investigate the clinical diagnosis and differential diagno- sis of synovial sarcoma (SS). METHODS A total of 41 paraffin-embedded synovial sarcoma samples were examined by H&E staining, immunohistochemistry staining and the re- verse transcriptase polymerase chain reaction (RT-PCR), in order to provide a scientific bases for diagnosis and differential diagnosis. RESULTS Twelve cases were a biphasic type, 22 cases were a mono- phasic fibrous type, and 7 cases were a poorly differentiated type. Thirty-six cases were both CK (and/or EMA) and Vim positive. Five cases were only Vim positive. A SYT-SSX fusion gene was detected in 18 cases by RT-PCR. CONCLUSION By observation of the histomorphology, immunohisto- chemistry markers and detection of a SYT-SSX fusion gene, we can make a clinical pathological diagnosis of synovial sarcoma. OBJECTIVE To investigate the clinical diagnosis and differential diagnosis-sis of synovial sarcoma (SS). METHODS A total of 41 paraffin-embedded synovial sarcoma samples were examined by H & E staining, immunohistochemistry staining and the re- verse transcriptase polymerase chain reaction ), in order to provide a scientific database for diagnosis and differential diagnosis. RESULTS Twelve cases were a biphasic type, 22 cases were a mono- phasic fibrous type, and 7 cases were a poorly differentiated type. Thirty-six cases were both CK and / or EMA) and Vim positive. Five cases were only Vim positive. A SYT-SSX fusion gene was detected in 18 cases by RT-PCR. CONCLUSION By observation of the histomorphology, immunohisto- chemistry markers and detection of a SYT-SSX fusion gene, we can make a clinical pathological diagnosis of synovial sarcoma.