An autopsy case of pulmonary artery leiomyosarcoma

A case of pulmonary artery leiomyosarcoma in a 37 year old Japanese man is reported. The patient complained of chest pain and hemosputum. CT scan and angiography revealed that a tumor arose from the right main branch of the pulmonary artery. The surgical specimen was interpreted as an undifferentiated sarcoma at this time. The tumor recurred 6 months after the resection, and he died of right-sided heart failure. At autopsy, the pulmonary artery truncus was distended by the tumor, which protruded into the lumen. The tumor was composed of pleomorphic cells, giant cells and spindle-shaped cells. Many of the tumor cells were immunohistochemically positive for alpha-smooth muscle actin and vimentin. Electron microscopy revealed microfilaments with dense bodies in the cytoplasm and a discontinuous basement membrane around the cells. Although adenocarcinoma was also observed in the colon, the authors conclude that the present tumor is not a metastasis but a primary leiomyosarcoma arising from the pulmonary artery. Imaging techniques were very useful for differentiating sarcoma from thrombus in this site, and immunohistochemical demonstration for alpha-smooth muscle actin was necessary for making a histological diagnosis of leiomyosarcoma.