[Rare Case of Thymic Epidermoid Cyst;Report of a Case].

A 68-year-old man with a mediastinal tumor was admitted to our hospital for surgical treatment. Chest computed tomography (CT) showed a 33×20×20 mm mass in anterior mediastinum. Magnetic resonance imaging (MRI) showed a heterogeneous structure in the cystic component of the mass. We diagnosed the tumor as thymic cyst preoperatively, and thymectomy was performed. The tumor was histopathologically diagnosed as thymic epidermoid cyst.