Giant idiopathic thymomegaly.

Apart from the anterior mediastinal position and the usual size of the normal thymus, aberrant locations and extreme size variations may occur. This is illustrated by an eight month old boy whose histologically normal thymus presented as a large mass in the right hemithorax. It is the largest normal thymus on record in an infant. Thus, idiopathic thymomegaly should also be considered in the differential diagnosis of peripheral intrathoracic mass lesions.