Posterior Intercostal Arteriovenous Malformation Mimicking a Pleural Mass: A Diagnostic Pitfall

ABSTRACT Intercostal arteriovenous malformations (AVMs) are rare, particularly in congenital cases. We report a 29‐year‐old man with no history of chest trauma who presented with left‐sided chest pain for 3 months. Initial routine contrast‐enhanced chest computed tomography (CT) revealed a pleural mass‐like lesion. Ultrasound‐guided biopsy was initially considered. However, pre‐biopsy chest ultrasound revealed pulsatile vascular flow within the lesion, raising suspicion for a vascular malformation. Subsequent CT angiography (CTA) demonstrated tortuous vessels supplied by multiple intercostal arteries with venous drainage into the intercostal veins and azygos system, confirming a congenital posterior intercostal AVM. Given persistent symptoms and surgical complexity, transarterial embolization with Onyx and N‐butyl cyanoacrylate (NBCA) resulted in marked shunt reduction and symptomatic improvement. This case reminds clinicians to consider intercostal AVMs in the differential diagnosis of pleural‐based lesions and reports our experience with endovascular embolization.