Synovial sarcoma most commonly occurs in the peri-articular regions of the extremities. We report a case of primary pulmonary monophasic synovial sarcoma. This tumor is extremely rare and shows a particular immunohistochemical pattern of great help for the diagnosis. Cytogenetic study confirm the diagnosis by showing the specific t (X; 18) chromosomal translocation, characteristic of synovial sarcoma in all anatomic locations.