Desmoid tumor of the sternum presenting as an anterior mediastinal mass.

A 20-year-old man with a large, asymptomatic mediastinal mass was found to have desmoid-type fibromatosis (DF) by needle biopsy. The tumor arose from the internal periosteum of the sternum and mimicked an anterior mediastinal mass. A wide resection of the sternum, including portions of the clavicles and costal cartilages, and reconstruction with a Gore-Tex soft tissue patch were performed. Although extremely rare, desmoid tumor of the sternum should be considered in the differential diagnosis of anterior mediastinal tumors.