The mean age at diagnosis of type B3 thymoma is around 55 years with a slight male predominance. About 50% of patients present with myasthenia gravis. Rarely, they may present with other autoimmune diseases such as pure red cell aplasia or hypogammaglobulinemia. The may have symptoms related to compression of anterior mediastinal structures (dyspnea, cough, chest pain) and fever, night sweats, and weight loss. Type B3 thymomas are more likely to present at advanced stages than other types of thymomas. They frequently invade beyond capsule into the surrounding fat or adjacent mediastinal structures. This low power image shows solid sheets of neoplastic epithelial cells with focal cystic changes.