Giant azygos vein varix.

Primary anomalies of the azygos vein generally result from intrathoracic tumor compression or inferior vena caval interruption with azygos vein continuation. Vascular malformations, although uncommon, can frequently mimic solid tumors and present as middle or posterior mediastinal masses. We present the case of an isolated giant azygos vein varix in an asymptomatic patient. Preoperative computed tomography and magnetic resonance imaging were not diagnostic in evaluating this patient's anatomy.