Pulmonary artery pseudoaneurysm arising from primary lung neoplasm: A proposed mechanism.

Pulmonary artery pseudoaneurysms (PAPs) are rare and life-threatening occurrences. We present a 57-year-old male patient with squamous cell lung cancer, who presented with hemoptysis. Bronchoscopy did not reveal ongoing bleeding. Imaging showed a left lower lobe tumor, a cavitary lesion communicating with the bronchus, and a pulmonary artery pseudoaneurysm. Successful embolization of the originating segmental branch of the pulmonary artery was performed. The pathogenesis of PAPs associated with primary lung malignancies remains poorly understood. We propose a four-step mechanism involving primary tumor expansion, central cavitary necrosis, direct arterial invasion, inflammatory response, vessel wall damage, pseudoaneurysm formation, and subsequent filling of the former cavitary lesion. This case emphasizes the importance of considering PAPs in primary lung malignancies, particularly in male patients with squamous cell pathology. Understanding the proposed pathogenic mechanism could lead to early detection, prompt intervention, and improved outcomes.