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