The risk of developing papillary thyroid cancer after therapeutic external radiation, used in the past to treat children with benign head and neck conditions, is well known.5 Exposure before the age of 15 years poses a major risk that becomes progressively greater with increasing amounts of radiation between 0.10 Gy (10 rad) and 10 Gy (1000 rad). This increases the incidence of thyroid carcinoma within 5 years of exposure, and this increased incidence continues for 30 years, at which time it begins to decline.5 Girls are only slightly more likely than boys to develop thyroid carcinoma after irradiation.5