A 58-year-old man was admitted with a month’s history of exertional dyspnea, which had been worsening for twenty days. The patient was being medicated for diabetes mellitus and hypertension. He was relatively stable, at New York Heart Association functional class II-III. On physical examination, the patient exhibited tachypnea, with 20 breaths per minute and his oxygen saturation was 92%, his pulse was regular at 95 beats per minute, and his blood pressure was 130/80 mmHg. Auscultation revealed a prominent second heart sound and grade 3/6 systolic murmur over the pulmonary area. A blood count revealed platelets at 57,000/mm3, but the rest of the work-up revealed no hematologic evidence of intrinsic hypercoagulability. The N-terminal pro-B-type natriuretic peptide level was 395 pg/ml (normal range: 0–125) and D-dimer was 0.816 μg/ml (normal range: 0–0.5). The chest radiograph revealed atherosclerotic cardiovascular change and mild cardiomegaly. Electrocardiography showed a sinus rhythm.
Evaluation with transthoracic echocardiography demonstrated a left ventricular ejection fraction of 56%. The right ventricle was enlarged and severely hypokinetic with a mobile echogenic mass in the supravalvular area of the main pulmonary artery. The color Doppler revealed a moderate tricuspid regurgitation. The systolic pulmonary arterial pressure was estimated with 70 mmHg. Subsequent evaluation with contrast-enhanced computed tomography (CT) of the chest demonstrated a large filling defect within the main pulmonary artery, which extended to near total occlusion of the left and right pulmonary artery, separately (Figure 1). There had been no intraluminal mass of the pulmonary artery on a chest CT 8 years earlier. Cardiac magnetic resonance imaging confirmed the mass beginning near the pulmonic valve, centered in the main pulmonary artery and extending into the right ventricular outflow tract, and onto both pulmonary arteries. A bilateral lower-extremity venous duplex scan was negative for acute deep venous thrombosis. Lung scintigraphy showed no visualization of the right lung on a technetium-99 m (99mTc-MAA) perfusion scan, but a ventilation scan showed no evidence of a ventilation defect, which was consistent with ventilation perfusion mismatch.
For the differentiation of the pulmonary artery mass between the thrombus and neoplasm, 18F-fluorodeoxyglucose uptake in positron emission computed tomography (FDG-PET) was performed to confirm the neoplastic features and the distant metastatic extent of the disease. The results of the FDG-PET showed a large mass, but no definite uptake in the mass, and no other hypermetabolic lesions were noted elsewhere (Figure 2). Our presumptive diagnosis was a massive mural thrombus and concomitant chronic thromboembolic disease. Intravenous heparin and recombinant human tissue-type plasminogen activator were subsequently administered.
After one day, the clinical presentation of the patient with progressive dyspnea and signs of congestive heart failure led us to decide on an emergent surgical approach. The patient was placed under general anesthesia. A standard median sternotomy and cardiopulmonary bypass was performed with aortic arterial and bicaval venous cannulation. After the aorta was clamped, cold blood cardioplegia was infused. The outer surface of the pulmonary arteries revealed no pathologic features, and longitudinal pulmonary arteriotomy was performed. In the lumen of the main pulmonary artery, a multilobulated whitish-yellow mass (Figure 3) was seen, and most of it involved the vascular inner wall. The main pulmonary artery was almost completely occluded by the mass and the mass had partially adhered to the pulmonic valve annulus. The small polypoid mass presented on the right ventricular outflow tract, and the main mass extended distally to both main pulmonary arteries. The main mass was resected along with part of the pulmonary artery wall but the pulmonary valve annulus was treated by curettage only and the leaflets were preserved. The small mass on the right ventricular outflow tract was resected through the pulmonary valve. The remaining masses on both branched pulmonary arteries were also resected. The defect in the pulmonary artery was repaired with a bovine pericardium patch. Even though as much as possible of both distal pulmonary artery masses were removed, there was no backflow from the right pulmonary artery and scanty backflow from the left pulmonary artery.
The intraoperative frozen biopsy was suggestive of sarcoma. We tried weaning the patient from cardiopulmonary bypass, but had to use extracorporeal membrane oxygenation (ECMO) due to the unstable vital status.
Permanent histological findings revealed a non-distinctive myxoid spindle cell sarcoma with a rather lobulated, exophytic growth pattern. Some mitotic activity was seen and pleomorphic tumor cells surrounded the endothelium, in particular (Figure 4). It was also highly malignant, but its cellularity was decreased with marked interstitial myxoid tissue. Immunostains showed multifocal positivity for smooth muscle actin, as well as focal positivity for desmin, consistent with myofibroblastic differentiation, while CD34 and S-100 protein were negative.
Given the poor prognosis and inability to wean the patient from the ECMO, we decided to withdraw the life support system after 5 days.