Pulmonary embolism or pulmonary artery intimal sarcoma? Diagnostic pitfalls in a rare vascular malignancy

Pulmonary artery obstruction is commonly attributed to pulmonary embolism; however, rare malignant conditions may present with similar clinical and radiological findings. Failure to recognize these alternative diagnoses may result in inappropriate treatment and delayed management. We report the case of a 48-year-old man presenting with acute dyspnoea and cough. Computed tomography angiography revealed a filling defect in the right main pulmonary artery, and pulmonary embolism was diagnosed. Despite appropriate anticoagulant therapy, the patient's clinical condition progressively deteriorated. The absence of deep vein thrombosis and the lack of right heart strain prompted diagnostic reconsideration. Endobronchial ultrasound-guided fine-needle aspiration revealed malignant spindle cell proliferation, and immunohistochemistry confirmed pulmonary artery intimal sarcoma. This case highlights the importance of reconsidering the diagnosis when clinical improvement does not occur despite adequate anticoagulation. Pulmonary artery obstruction should not automatically be attributed to thromboembolism, and malignancy must be considered in the differential diagnosis. LEARNING POINTS: Pulmonary artery obstruction should not automatically be attributed to thromboembolism, as rare malignancies may present with similar findings.Lack of clinical improvement despite appropriate anticoagulant therapy should prompt immediate diagnostic reconsideration.