Ectopic functioning thyroid tissue in the thyroglossal duct detected by radionuclide imaging.

A 49-year-old man with a clinical diagnosis of Graves' disease was referred for a thyroid scan and radioactive ablation of the gland. Tc-99m pertechnetate scan revealed a diffuse toxic goiter and radiotracer concentrationin the thyroglossal duct. He was given 10 mCi of 1-131 orally as treatment of thyrotoxicosis. Repeat scanning of the anterior neck 2, days later revealed concentration of radioiodine in the diffusely enlarged gland and the thyroglossal duct as found on the Tc-99m pertechnetate scan, thus confirming the presence of functioning thyroid tissue in the thyroglossal duct.