Monophasic synovial sarcoma presenting as mitral valve obstruction.

We report the case of a 26-year-old man who experienced progressive left-sided chest pain and 2 episodes of near-syncope. Studies revealed a 15-cm mass in the upper left lung, a 10-cm mass in the medial base of the left lung, and a 5-cm left atrial mass that involved the left lung, infiltrated the left pulmonary vein, and prolapsed into the mitral valve, causing intermittent obstruction. The patient underwent surgical excision of the left atrial tumor. Pathologic evaluation confirmed the diagnosis of monophasic synovial sarcoma.To our knowledge, this is only the 3rd report of left atrial invasion and resultant mitral valve obstruction from a synovial sarcoma that infiltrated the pulmonary vein. We believe that this is the 1st documented case of a metastatic left atrial synovial sarcoma in monophasic form.