A Challenging Case of Hyperfunctioning Submandibular Ectopic Thyroid Successfully Treated With 131I

Abstract Ectopic thyroid tissue is a rare condition, caused by aberrancy during thyroid gland embryogenesis. Any pathology involving the thyroid gland can also affect the ectopic tissue, including tumorigenesis. We report a challenging case of relapsed hyperthyroidism in a woman who already underwent subtotal thyroidectomy in 1995 and surgical revision in 2020 for multinodular toxic goiter. 99m Tc-pertechnetate scan revealed an area of radiotracer focal uptake at submandibular level, posing a differential diagnosis between salivary gland tumor and ectopic thyroid. Correlation with clinical history and ultimately histopathology led to diagnosis of hyperfunctioning submandibular ectopic tissue, successfully treating the patient with 131 I.