Abstract
Thymomas are typically located in the anterior mediastinum and are rarely identified in other locations. A 48-year-old male patient was admitted to the hospital due to myasthenia gravis (MG). A mass in the middle mediastinum, obstructing the superior vena cava, was revealed by computed tomography and magnetic resonance imaging examination. The postoperative diagnosis was thymoma type AB, stage III. After surgery, he was treated with radiation therapy neoadjuvant. At the 5-year follow-up, recurrence was not observed. Ectopic thymoma in the middle mediastinum has been reported in 26 other cases in the literature. Most were classified as thymoma type A or AB, and all were stage I or II. Most of them were located in the upper right mediastinum, adjacent to the right trachea, and in the retro innominate vein area. Thymoma should be considered a differential diagnosis when a mass is observed in the middle mediastinum.