ACCOMPANYING TEXT
A 41-year-old female patient was referred to the department of head and neck surgery due to a large submandibular midline mass that had been present since childhood but had progressively increased in the three months prior to referral. [Image 1] CT scan of the neck[Image 2] described the lack of eutopic location of the thyroid gland, scintigraphy indicated that functional thyroid tissue was located only in the submandibular mass, and FNAC was diagnostic for benign thyroid tissue. Thyroid function blood tests (TSH and thyroxine) were normal. A multidisciplinary team of physicians decided for surgical resection, which included the hyoid bone and adjacent muscles due to the proximity of the submandibular mass. [Images 3 and 4] The anatomopathological evaluation confirmed thyroid tissue without any malignant characteristics present.
Ectopic location of the thyroid gland is a rare event, with a reported prevalence of 1:100,000 to 1:300,000 in the general population. [1] This anomaly is due to the embryological development of the thyroid gland from the base of the tongue to its normal eutopic location in the lower third of the neck, just anterior to the trachea. [1] Ectopic location in the trachea, thorax, and abdomen has also been reported. [2]
Submandibular neck masses present a broad differential diagnosis, with emphasis on neck malignant disease that must be excluded. [2] Although malignancy is rare in ectopic thyroid tissue, this diagnosis should be kept in mind whenever a patient presents with a neck mass. [1-3] Also, as it is the case in more frequent midline neck masses, such as in thyroglossal duct cysts, it is important in the diagnostic workup to exclude the presence of ectopic thyroid tissue, which may represent the patient’s only functioning thyroid. [3]