Thymic cyst: computed tomography and ultrasound correlation.

Thymic cyst is a rare cause of an anterior mediastinal mass that cannot be easily differentiated from more sinister neoplastic anterior mediastinal processes on the chest radiograph. It is controversial as to whether computed tomography can make the distinction between thymic cysts and neoplastic disease. Sonography is a useful adjunct to the computed tomographic examination in determining whether or not an anterior mediastinal mass is cystic. Sonography is easily performed provided the mass is in contact with the chest wall.