Normal and abnormal vascular structures that simulate neoplasms on chest radiographs: clues to the diagnosis.

Despite increased use of and reliance on cross-sectional imaging techniques in the thorax, conventional chest radiography remains the most commonly performed imaging examination. However, conventional radiographic appearances of normal and abnormal vascular structures can be misinterpreted as representing neoplasms or soft-tissue masses and lead to inappropriate diagnostic procedures. Vascular structures that can simulate neoplasms include normal structures such as the subclavian artery and left brachiocephalic, azygos, and pulmonary veins and abnormal structures such as congenital and acquired anomalies of the thoracic aorta and its branches, pulmonary arteries and veins, superior and inferior venae cavae, and azygos and hemiazygos veins. Other entities such as postoperative changes, massive pulmonary embolism, false ventricular aneurysm, and esophageal varices can also be misinterpreted. Important radiographic features that help distinguish these vascular structures from true neoplasms include proximity to known vascular structures, smooth margination, mural calcification, round or oval configuration, poor or nonvisualization in one of two orthogonal views, and absence or altered position of normal vascular structures. Knowledge of patient history and a detailed understanding of normal mediastinal anatomic structures and common variants help in making the correct diagnosis. Familiarity with these entities will result in the proper, most cost-efficient evaluation.