A case report of pulmonary artery intimal sarcoma negative for 18F-FDG mimicking pulmonary thromboembolism.

Background: Pulmonary artery sarcoma is a rare malignant neoplasm arising from intimal mesenchymal cells in the pulmonary artery wall and is often difficult to differentiate from pulmonary embolism, however, 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) can be useful for a differential diagnosis. Here, we present a rare case of pulmonary sarcoma undetectable by PET. Case summary: A 77-year-old woman who had worsening dyspnoea on effort for a month and progressive chest discomfort with nocturnal cough for a week presented to our hospital. Contrast-enhanced computed tomography (CT) demonstrated a massive filling defect in the left pulmonary artery (PA). Two major differential diagnoses were considered; pulmonary thromboembolism and tumour-like lesions. Positron emission tomography-computed tomography (PET-CT) revealed that there was no abnormal accumulation of 18F-FDG in the mass. However, even after effective anti-thrombotic treatment for 3 weeks, a follow-up CT showed no reduction at all in the size of the lesion in the pulmonary artery. Therefore, surgery for diagnostic therapeutic purposes was performed. Discussion: The present case is informative because it supports the idea that being aware of PA angiosarcoma as a potential differential diagnosis of pulmonary thromboembolism is essential, particularly in cases of no evident peripheral venous thrombosis and a negative D-dimer test, even if neither heterogenous contrast enhancement in CT and magnetic resonance imaging nor accumulation of 18-FDG in PET-CT is evident.