While newly recognized neck masses in children previously treated for malignancy raise the specter of recurrent disease, recent experience with 2 patients has shown us that enlargement of cervical thymic tissue should be considered in the differential diagnosis, especially early after the completion of chemotherapy or immunotherapy. While newly recognized neck masses in children previously treated for malignancy raise the specter of recurrent disease, recent experience with 2 patients has shown us that enlargement of cervical thymic tissue should be considered in the differential diagnosis, especially early after the completion of chemotherapy or immunotherapy.