A tumor of the thymus gland. An asymptomatic thymoma is usually detected as an incidental finding on a chest x-ray, where it appears as a mediastinal mass. Symptomatic thymomas typically present in individuals between 40–60 years of age with thoracic symptoms (e.g., chest pain, cough, dyspnea) or paraneoplastic syndromes, the most common of which is Myasthenia gravis. Treatment options include surgery, chemotherapy, and/or radiotherapy.