A case of idiopathic azygos vein aneurysm and review of the literature.

Azygos vein aneurysm is extremely rare. Herein we report a 41-year-old woman whose chest radiograph showed right paratracheal opacity. During 6-month follow-up, she underwent computed tomography scanning 3 times and magnetic resonance imaging. The mass enlarged gradually and changed its position from the posterior to the anterior upper right mediastinum. Venography and surgery were finally performed, which confirmed an aneurysm of the azygos vein. Pathologic findings indicated a congenital etiology. To the best of our knowledge, such an azygos vein aneurysm with changeable position during follow-up has not been reported previously.