ABSTRACT
Perfusion scintigraphy has proved to be an essential part for the diagnosis of pulmonary thromboembolism. The wedge shaped perfusion defect extending to lung base is a highly probable finding of pulmonary embolism. Occasionally, great perfusion defects could be presented as a false positive finding under the circumstance of nonthromboembolic origin, such as neoplastic compression or invasion of pulmonary artery. We report an unusual case of massive perfusion defect resulting from pulmonary arterial compression by bronchogenic carcinoma. A 71-year-old man visited our hospital because of productive cough and was diagnosed as bronchogenic carcinoma. The perfusion scintigraphy showed unilateral total defect of lung, not accompanied by any clinical evidence of thromboembolism. A contrast enhanced computed tomogram showed heterogeneous mass shadow in left hilum, abutting to the descending aorta and compressing left main pulmonary artery. These findings suggested a nonembolic mechanism of perfusion defects which were produced by the neoplastic compression of pulmonary artery.