Primary Pulmonary Vein Leiomyosarcoma With Left Atrial Extension.

Leiomyosarcoma (LMS) is a mesenchymal tumor originating from the smooth muscle cells. LMS of the great vessels accounts for 60% of cases, with inferior vena cava being the most common site. Pulmonary vein LMS is an extremely rare subset that was first reported in 1939.