C44-29 Incidental Azygos Vein Aneurysm Presenting as a Mediastinal Mass

Introduction Azygos vein aneurysm (AZA) is a rare venous malformation that may mimic a mediastinal mass. Recognition of this benign entity is critical to avoid unnecessary invasive procedures. We report an incidental case of AZA identified during evaluation for unrelated symptoms. Case Presentation A 68-year-old woman presented with confusion and slurred speech. Laboratory findings were unremarkable except for mild hypercapnia. Head and neck CT/CTA showed no acute intracranial pathology but incidentally revealed a right paratracheal mass. Chest CTA demonstrated a 2-cm lobulated soft-tissue density in the right lower paratracheal region without lung nodules or lymphadenopathy. MRI confirmed an azygos vein aneurysm. The patient denied respiratory symptoms. Given the stable imaging features and lack of symptoms, conservative management with low-dose aspirin and radiologic follow-up was chosen. Discussion AZA is an uncommon vascular anomaly that may be congenital or acquired secondary to trauma, portal hypertension, arteriovenous fistula, or elevated venous pressure. Most cases are detected incidentally during imaging for unrelated conditions. Symptomatic presentations may include cough, dyspnea, or chest pain from compression of adjacent structures. Rarely, complications such as thrombosis, rupture, or pulmonary embolism may occur. Recognition on imaging helps distinguish AZA from lymphadenopathy or mediastinal tumors. Conclusion Azygos vein aneurysm, though rare, should be considered in the differential diagnosis of right mediastinal masses. Accurate radiologic identification can prevent unnecessary biopsies or surgical interventions and supports safe conservative management when asymptomatic.