Thymic Adenocarcinoma Presenting Late as a Large Subcarinal Mass

Thymic malignant neoplasms mostly occur in the anterior mediastinum. Less than 5% occur in the middle or posterior mediastinum. This report describes a large subcarinal mass incidentally discovered during follow-up magnetic resonance imaging for prostate cancer operation. After multidisciplinary discussion, chemotherapy was deemed ineffective, and complete tumor resection through right posterolateral thoracotomy was performed. The operation was uneventful, and the patient recovered smoothly. Immunohistochemistry and pathologic examination revealed thymic adenocarcinoma. Although very rare, thymic adenocarcinomas should be considered in the differential diagnosis of middle mediastinal masses.