Background: Ectopic thyroid tissue in the submandibular region is exceptionally rare. Nevertheless, the treating physician should consider this condition within the differential diagnosis of a submandibular mass.
Method: Case report of ectopic thyroid tissue presenting as a submandibular mass in a patient with hyperthyroidism, together with a review of the English-literature concerning ectopic thyroid tissue.
Conclusion: To our knowledge, this is the first report of ectopic thyroid tissue presenting as a submandibular mass and causing hyperthyroidism. Removal of the submandibular mass resulted in normalisation of thyroid function, and subsequent reduction in the patient's antithyroid medication dosage. Ectopic thyroid tissue should be suspected in any patient with a submandibular mass. Prior to resection of such a lesion, it is essential to ensure that normal, functioning thyroid tissue is present elsewhere. Ectopic thyroid tissue can also present with pathology similar to that affecting the normal thyroid gland.