From the Archives of the AFIP

mediastinal mass of variable size and may be helpful in the evaluation of adjacent structures in cases of invasive thymoma. The treatment of choice is complete surgical excision. Radiation therapy and chemotherapy may be used adjunctively to surgery in the treatment of invasive tumors. The prognosis of encapsulated thymoma is generally favorable. Invasive tumors are associated with a worse prognosis but may respond to radical resection. U INTRODUCTION Thymomas are epithelial neoplasms of the thymus and the most common primary neoplasms of the anterior superior mediastinum. They usually occur in adults. The tumor may be completely encapsulated or may display various degrees of invasion of the tumor capsule and the adjacent structures. In this article, we review the histologic types and gross features of thymoma as well as its clinical presentation, therapy, and prognosis. The various radiologic featunes of thymoma are illustrated with emphasis on nadiologic-pathologic correlation.