CASE PRESENTATION: A 29 year old man smoker presented with dyspnea, chest pain and hypoxemia. He denied long travels, drug use and medical history was relevant for Asthma. Acute PE involving main and left pulmonary arteries was diagnosed (Fig. 1). An Echocardiogram, DVT and hypercoagulable studies were normal. He was discharged on Rivaroxaban. A month later, he's back with recurrent symptoms; a CTPA showed new multiple bilateral pulmonary nodules and cavitations. He denied constitutional symptoms. Examination showed a well appearing man; SaO2 of 97% on room air; chest, heart and skin exam were normal. Laboratory tests showed eosinophilia of 10% and ESR at 94 MM/HR. Connective tissue disease and ANCA antibodies work up were negative. Unfractioned heparin was started. Repeated CTPA showed increased clot burden, pulmonary nodules and ground glass opacities(Fig. 2).Trans-bronchial biopsies via electromagnetic navigational bronchoscopy resulted in benign lung tissue. A right heart catheterization showed mildly elevated PA pressures, normal PCWP and CO. Trans-pulmonary pressure gradient was19 and PVR 3.82 WU. Cardiothoracic surgery service proceeded with pulmonary thrombo endarterectomy and lung biopsy. A mass involving the main and left pulmonary arteries was found with chronic thrombo embolic disease. Pathology revealed high grade/advanced intimal pulmonary artery sarcoma positive for Vimentin and FLI-1; negative for S-100, CD 31, CD 34, SMA, AE1/AE3 and Actin. Systemic chemotherapy was advised.