Huge mediastinal cystic tumor penetrating the sternum.

We report a very rare case of a huge anterior mediastinal tumor penetrating the sternum that was diagnosed in a 59-year-old woman. The tumor was completely resected en bloc with the manubrium sterni, and the chest wall defect was closed with a pectoralis major muscle flap. Histologic examination of the cystic mass revealed the diagnosis of a benign mediastinal cystic tumor, most likely a benign cystic mature teratoma.