Triple-Site Ectopic Thyroid Involving the Submandibular, Lingual, and Infrahyoid Regions: A Rare Case.

Thyroid gland development normally begins in utero during the fourth week of pregnancy. It advances to its definitive anatomical location, situated between the second and fifth tracheal cartilages, often by seven weeks of gestation. An ectopic thyroid gland is characterized by its unusual location, which results from abnormal embryonic development. A 34-year-old female patient presented to the ENT department, primarily complaining of painless swelling in the right submandibular region that had been present for nine months. This swelling was insidious in onset and gradually progressive, with a notable increase in size occurring over the last three months. The patient has a documented history of hypothyroidism and is now undergoing treatment. The results of thyroid function testing indicated that the level of thyroid-stimulating hormone was 6.107 µIU/mL, total triiodothyronine was 1.269 ng/mL, and total thyroxine was 11.197 µg/mL. Radiological imaging modalities, such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) scans of the neck, showed a complex, thick-walled cystic lesion adjacent to the right submandibular gland, measuring 3.9 x 3.0 cm, with thick internal septa and another well-defined solid lesion in the right infrahyoid region. The CT and MRI scans revealed another round solid lesion at the base of the tongue. Normal thyroid gland tissue was not seen at its native place. Scintigraphy was not performed due to a recent use of an iodinated contrast medium for contrast-enhanced CT. The patient underwent ultrasound-guided fine-needle aspiration cytology (FNAC) for the right submandibular lesion; however, the cytology was non-diagnostic due to the predominant cystic component and rich vascularity. Because of suspicion of malignancy, non-diagnostic cytology, and a recent increase in the size of the swelling, the submandibular and infrahyoid lesions were completely surgically resected. Histopathology revealed cystic colloid tissue with benign thyroid cells displaying oncocytic changes and normal thyroid tissue in the submandibular and infrahyoid lesions. The patient was ultimately diagnosed with multifocal benign ectopic thyroid tissue without malignant transformation. The patient was instructed to continue with the medication for hypothyroidism. The purpose of this case report is to present a very rare case of triple-site ectopic thyroid involving the submandibular, lingual, and infrahyoid regions, emphasizing the value of considering ectopic thyroid as a differential diagnosis in submandibular, infrahyoid, and lingual masses, particularly in the absence of an orthotopic gland.