What is a thymoma?

Thymoma is a tumor arising from thymic epithelial cells and is a type of primary tumor of the anterior superior mediastinum. It accounts for approximately 20% to 40% of all mediastinal tumors in adults, with the majority located in the anterior mediastinum, attached to the pericardium. Thymomas grow slowly and are mostly benign, but they possess potential invasiveness and tend to infiltrate surrounding tissues and organs. Thymomas are closely associated with autoimmune disorders and are frequently accompanied by various paraneoplastic syndromes, such as myasthenia gravis. Thymomas can be classified into types A, AB, B1, B2, B3, and C, with type C being thymic carcinoma, characterized by marked cellular atypia and loss of the specialized thymic architecture. The exact pathogenesis of thymoma remains unclear, but it may be related to Epstein-Barr virus infection and a history of radiation therapy.