Lingual thyroid.

Lingual thyroid is one of the rarest anomalies of thyroid origin. It is located in the midline of the base of the tongue. Lingual thyroid répresents ectopic, i.e. accessory thyroid tissue. It develops from the epithelium of the thyroglossal duct that has not obliterated properly, and it is sometimes the only thyroid tissue. Beside two cases presented, the embryology, symptomatology, diagnostic and therapeutic procedures, the literature reports of lingual thyroid are reviewed.