Rebound thymic hyperplasia five years after chemotherapy for Wilms' tumor.

Rebound thymic hyperplasia following chemotherapy is well documented, usually occurring within the first year. A delayed presentation makes distinction from an anterior mediastinal mass problematic in view of the increased risk of a second primary malignancy in pediatric cancer survivors. An unusual case of rebound thymic hyperplasia is described, presenting five years after completion of chemotherapy for Wilms' tumors.