Diagnostic value of plain chest roentgenogram and CT scan findings in four cases of massive thymic hyperplasia.

Massive thymic hyperplasia (MTH) is rare in the pediatric age group, especially in infants. However, because of a wide variation in size and weight of the thymus, an enlarged gland is often resected because of suspicion of a neoplasm or a cyst. Some cases of thymoma resembling pulmonary acute infection occur less frequently than MTH, but if respiratory problems are accompanied by a large thymus immediate diagnosis is often necessary to differentiate between these two conditions. Four infants (14 days to 4 months of age) with MTH were recently studied, all having an acute onset of a severe respiratory distress. The infants were referred to our center with a tentative diagnosis of thymic or other intrathoracic tumors. The following case reports illustrate our diagnostic approach to evaluate patients with symptoms suggesting MTH and the response to the "steroid test".