Abstract: A retrospective study was performed in 2 cases of primary pulmonary synovial sarcoma (PPSS) with short course of the disease. Chest CT scan showed that the lung mass had the characteristics of definite boundaries, uneven density distribution, and heterogeneous  enhancement on CT  enhanced scan. Pathological examination showed the dense proliferation of spindle cells with less cytoplasm, higher nucleoplasmic ratio, fine chromatin, inconspicuous nucleoli, and mitotic figure. Immunohistochemistry revealed that the cells were positive for epithelial membrane antigen(EMA), vimentin, CD99 and CK, negative for CD34,  Actin,  S100 and Desmin, and partially positive for Ki67. Cytogenetics showed SS18 gene fragmentation test (FISH method) was positive. Conclusively, the diagnostic level of PPSS can be improved with the combination of  chest  CT sacn, pathological examination, immunohistochemistry and the examination of fusion gene.

Key words: sarcoma, synovial, lung; , chest ct scan; , pathological features, immunohistochemistry, fusion gene