We report on a 59-year-old male patient who suffered from dyspnea, cough and hemoptysis. Initial chest X-ray revealed a prominent right pulmonary artery (RPA) and MR imaging showed a "filling defect" within the main pulmonary trunk and RPA indicating pulmonary thromboembolic disease. Despite systemic anticoagulation, symptoms progressed. Follow-up CT showed an enlarging "filling defect" with additional extension into the left pulmonary artery as well as multiple intrapulmonary nodules. Lesion biopsy revealed a pulmonary artery angiosarcoma. Imaging findings are presented. Our case illustrates that pulmonary artery angiosarcoma should be included in the differential diagnosis of pulmonary thromboembolic disease in cases where a) symptoms do not respond to anticoagulation, b) no source of thrombi/emboli can be detected and c) pulmonary nodules/metastases develop on follow-up.