Preaortic interazygous vein; mimicker of other pathologies.

We present a case of preaortic interazygous vein found incidentally in a patient with a breast mass and back pain. Enhanced CT showed a vascular structure surrounding the left anterior portion of the thoracic aorta at the level of T8, which was continuous to the azygous vein on the right side and to the hemiazygous vein on the left. This finding represents preaortic interazygous vein crossing anterior to the aorta. This vascular variation, which is a very rare form of the azygous venous system, can mimic other mediastinal pathologies. We must take this vascular variation into consideration during CT interpretation.