MON-455 The Wandering Thyroid: A Case of Lingual Thyroid

Abstract Disclosure: V.E. Bravo: None. J.B. Aragon: None. Lingual thyroid is a rare condition resulting from the failure of thyroid tissue to migrate to its normal location during embryologic development, often presenting as ectopic thyroid tissue at the base of the tongue. It is typically asymptomatic but may cause symptoms such as dysphagia, dysphonia, and dyspnea, especially if the ectopic tissue enlarges. This case report presents a 31-year-old Filipino female with a painless submental mass that had increased in size over two years. Initially misdiagnosed as a thyroglossal duct cyst, imaging revealed a 3.8 x 4.1 x 4.0 cm hyperdense mass at the tongue base, with no thyroid gland in its normal location. Thyroid function tests were normal, and fine needle aspiration biopsy confirmed the diagnosis of lingual thyroid.Lingual thyroid is seen predominantly in females and is more common in patients of Asian descent. While most cases are asymptomatic, hypothyroidism is noted in approximately 70% of individuals, requiring thyroid function tests to guide management. Imaging modalities such as ultrasound and CT scan help identify ectopic thyroid tissue, and a biopsy provides definitive diagnosis. In this case, a thyroid scintigraphy scan was not performed due to financial constraints, but the workup was sufficient for diagnosis.Management depends on the presence of symptoms and thyroid function. As this patient was euthyroid and asymptomatic, conservative management with regular follow-up was recommended. Surgical excision may be indicated for symptomatic patients or those with suspected malignancy. This case emphasizes the importance of considering lingual thyroid in the differential diagnosis of neck masses and highlights the role of imaging, thyroid function testing, and biopsy in establishing the diagnosis. Regular monitoring is advised for asymptomatic, euthyroid patients. Presentation: Monday, July 14, 2025