Massive hyperplastic thymus in a 22-month-old infant.

Huge mediastinal masses in infants are often difficult to diagnose, and thymic enlargement must be considered in each instance, especially when the mass is located anteriorly. In the patient reported on here, the mass occupied approximately 60% of the chest cavity, and surgical intervention was required to establish the precise histological diagnosis. This proved to be massive hyperplastic thymus.