Angiomyolipomas are benign mesenchymal tumors consisting of blood vessels, smooth muscle, and fat. These noninvasive lesions characteristically manifest in renal tissue but may arise less frequently in extrarenal locations including the mediastinum. Only 8 cases of mediastinal angiomyolipomas have been reported in the literature, 3 of which were reported in the English literature, and only 2 of which were located in the anterior mediastinum. We report a surgically confirmed case of an anterior mediastinal angiomyolipoma incidentally discovered in an asymptomatic patient, in whom a screening breast magnetic resonance imaging revealed an incidental 5.7 cm anterior mediastinal mass. Further characterization with contrast-enhanced chest computed tomography confirmed a heterogeneously enhancing anterior mediastinal mass, suggestive of thymoma or lymphoma. The mass was resected and histopathologic evaluation revealed an angiomyolipoma. © 2007 Lippincott Williams & Wilkins, Inc.