Ectopic submandibular thyroid tissue.

: We reported a case of a 66 year-old male patient with a mass located in the right submandibular region. Surgical excision of the mass was performed and histologic examination revealed that the tumor was ectopic thyroid tissue. Additionally, imaging studies confirmed that the thyroid gland was found in its normal location and the patient had normal thyroid function testing. In reviewing the literature, we found submandibular thyroid tissue to be a rare entity with only 4 cases described. We discussed embryologic development of the normal thyroid gland and some explanations as to the origins of several forms of ectopic thyroid tissue, including that found in the submandibular region.