Resection continues to be the mainstay of treatment for epithelial lesions of the thymus. This has never been in doubt for encapsulated stage I and II lesions, but we recently have come to a greater appreciation of the role of preoperative therapy for locally advanced lesions, particularly stage III disease. For any lesion that presents in the anterior mediastinum and on CT scan does not appear to be eminently resectable, a biopsy should be performed to rule out lymphoma after serum germ cell markers have been obtained to rule out the rare primary mediastinal or metastatic germ cell tumor.