Pulmonary artery constriction by mediastinal lymphoma simulating pulmonary embolus.

Two cases of constriction of the pulmonary artery secondary to mediastinal lymphoma are reported. Both patients had clinical symptoms of pulmonary embolism. Radionuclide lung scans showed no perfusion of the right lung in one patient, and diminished perfusion of the right lung in the other. Pulmonary angiography revealed diffuse concentric narrowing of right main pulmonary arteries in both patients and of lobar branches in one, in whom severe encasement of the right pulmonary artery by a lymphomatous mass confirmed at autopsy. The decisive role of pulmonary angiography in determining the underlying pathology in patients with abnormal perfusion scans is illustrated.