Giant azygos vein aneurysm incidentally detected during breast cancer workup: a case report

Abstract

Azygos vein aneurysms are extremely rare vascular anomalies of the mediastinum. Most are asymptomatic and incidentally found during imaging. Their rarity, non-specific presentation, and radiologic resemblance to other mediastinal masses make accurate diagnosis challenging. This case adds to the limited literature and emphasizes the value of preoperative imaging in diagnosis and surgical planning.A 54-year-old woman was admitted for evaluation of a left breast mass. She had no cardiopulmonary symptoms. Preoperative contrast-enhanced CT revealed a well-defined, homogeneously enhancing posterior mediastinal mass (8.1 × 3.9 cm) in continuity with the azygos vein. Given the lesion’s size and unclear nature, surgical resection was performed via median sternotomy, with careful intraoperative handling to prevent thromboembolism. Pathology confirmed a thrombosed azygos vein aneurysm. Immunohistochemistry was positive for CD31, CD34, ERG, D2-40, calretinin, and WT-1, with a Ki-67 index <1%, consistent with a benign vascular lesion. The patient recovered well without complications. Azygos vein aneurysms, though rare, should be considered in the differential diagnosis of mediastinal masses. Cross-sectional imaging is essential for identifying vascular origin and planning safe resection. Surgical removal is indicated for large or uncertain lesions, particularly when thrombosis is present. Early diagnosis and intervention can prevent complications and offer definitive histological confirmation, especially in patients undergoing oncologic workup.