A female patient is described who developed papillary-follicular carcinoma of the thyroid 8 years after receiving high-dose external radiotherapy to the head and neck. This malignant neoplasm developed while she was taking suppressive doses of thyroid medication. Although it has long been thought that high-dose radiotherapy is not associated with the occurrence of thyroid tumor, it is becoming increasingly apparent that this concept is not necessarily true. Clinicians should be aware of the possible sequelae of neoplastic thyroid disease after any amount of external radiotherapy to the head and neck. Careful periodic follow-up of patients who have received such treatment is strongly advised.
