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Lingual thyroid (LT) gland is a rare clinical entity which was found to occur due to the failure of the thyroid gland to descend to its normal cervical location during embryogenesis. The presence of an ectopic thyroid gland located at the base of the tongue may present with symptoms like dysphagia, dysphonia, upper airway obstruction or even hemorrhage at any time from infancy through adulthood.
We are presenting a case of 5-year-old girl who presented with lingual thyroid, treated with Suppression treatment followed by elective surgical resection.
Incidence of ectopic lingual thyroid gland is reported as 1:100,000. It is more common in females. Most of presentations due to oropharyngeal obstruction, including dysphagia, dyspnea and dysphonia. Investigations include thyroid function tests, neck US, Technetium scanning and C.T.
Lingual thyroid is a rare anomaly. Dysphagia and dysphonia are common presenting symptoms. Pathogenesis of this ectopic is unknown. Different types of surgical approaches have been described in the management.
The thyroid gland is one of the largest endocrine glands in the body, it lies approximately the same level as the cricoid cartilage.1,2 Ectopic thyroid tissue has been found from the tongue to the diaphragm. Ninety percent of the reported cases of ectopic thyroid are found in the base of the tongue.14 Lingual thyroid is a rare developmental thyroid anomaly, caused by the failure of the gland to descend from its anlage, early in the course of embryogenesis. It generally originates from epithelial tissue of non-obliterated thyroglossal duct.9 Prevalence rates of LT vary from 1 in 100,000 to 1 in 300,000, with females to male ratio ranging from 4:1 to 7:1.12
Although the pathogenesis of lingual thyroid is unclear, some authors have postulated that maternal antithyroid immunoglobulins may impair gland descent during early fetal life.5 Clinical presentation is varying from mild dysphagia to severe upper airway obstruction. Diagnosis depends on finding thyroid tissue at the base of the tongue with the absence of normally located gland. Imaging studies as ultrasound scan, C.T scan and Technetium (Tc99m) thyroid scan would be of great value establishing the diagnosis.3 The treatment options for lingual thyroid include: levothyroxine suppression therapy, radioactive iodine ablation and lingual thyroidectomy. The decision between conservative and surgical therapy depends on subjective complaints, regional iodine uptake, growth behavior of the lingual thyroid and especially on cytological findings of fine needle biopsy.8
We present a case of a 5-year-old girl who was referred to the outpatient clinic, complaining of progressive dysphagia to solid foods. Her past medical history was insignificant. Her mother denied receiving any medications during pregnancy.
On physical examination, it was noticed that she had a 3 cm × 4 cm midline smooth, rubbery and reddish mass at the base of the tongue, with overlying telangiectasias (Figs. 1 and 2). Neck examination revealed neither palpable thyroid gland nor any other palpable masses.
Thyroid function tests demonstrated euthyroid levels. Other laboratory tests were within normal limits. Thyroid US scan revealed the absence of thyroid gland. Technetium (Tc99m) thyroid scan, revealed isotope uptake at the base of the tongue and no uptake in the normal thyroid location (Fig. 2). Fine needle aspiration biopsy from the mass revealed normal thyroid tissue with few colloidal changes.
The nominated final diagnosis was lingual thyroid (LT). Suppression treatment with thyroid hormone was given for 3 weeks followed by elective surgical resection of the gland via oral approach under general anesthesia induced via nasotracheal intubation was carried out, the patient passed a smooth post operative period, discharged on the fifth day post operatively on, levothyroxine 5 mcg/kg/day, seen in the clinic in 1 month, 3 month and 6 month intervals, found to be symptom free.
Hickmann recorded the first case of lingual thyroid in 1869. Montgomery stressed that for a condition to be branded as lingual thyroid, thyroid follicles should be demonstrated histopathologically in tissues sampled from the lesion.4 A brief discussion of embryology of thyroid gland would ensure better understanding of the pathophysiology involved in the formation of ectopic thyroid gland. Early in embryogenesis, thyroid gland appears as proliferation of endodermal tissue in the floor of the pharynx between tuberculum impar and hypobranchial eminence (this area is the later foramen caecum).9 Normally thyroid gland descends along a path from foramen cecum in the tongue, passes the hyoid bone, to the final position in front and lateral to the second, third, and fourth tracheal rings by 7 weeks gestation. During this descent thyroid tissue retains its communication with foramen cecum. This communication is known as thyroglossal duct. Once the thyroid reaches its final destination, the thyroglossal duct degenerates.8 Persistence of thyroglossal duct even after birth leads to the formation of thyroglossal cyst. These cysts usually arise from the remnants of thyroglossal duct and can be found anywhere along the migration site of thyroid gland. This descent may arrest anywhere along this path and this condition may remain unnoticed until puberty. Any functioning thyroid tissue found outside of the normal thyroid location is termed ectopic thyroid tissue.3 Although it is usually found along the normal path of development, ectopic tissue has also been noted in the mediastinum, heart, esophagus, and diaphragm. Lingual thyroid is the result of failure of descent of the thyroid anlage from the foramen cecum of the tongue. The reasons for the failure of descent are unknown.5
The incidence of LT is reported as 1:100,000. It is 7 times higher in females.10
Clinical presentations are varied, most of them related to oropharyngeal obstruction, and may include dysphagia (mild or severe), dyspnea and dysphonia, fullness in the throat, sleep apnoea. Stridor is most common in neonates.5 About 33% of the patients show hypothyroidism findings.5 Bleeding is rarely described.
The clinical presentation of LT could be classified into two groups according to the appearance of the symptoms: infants and young children whose lingual thyroid is detected via routine screening may suffer from failure to thrive and mental retardation, or even severe respiratory distress, resulting in a medical emergency.5,6 Other cases may present with onset of slowly progressing dysphagia and symptoms of oropharyngeal obstruction before or during puberty. This occurs as a response to the increased demand for thyroid hormone in these hypermetabolic states. Similar response is also encountered during other metabolic stress conditions like pregnancy, infections, trauma, menopause, etc.1 LT usually presents itself as a midline, nodular mass in the base of the tongue.9–11 The surface of the lesion is usually smooth and vascularity can be seen. This was the case in our patient. Thorough head and neck examination with special attention to the base of the tongue is mandatory. Palpation of the neck is extremely essential, in order to check the presence or the absence of the thyroid gland in its normal position. Investigations include thyroid function tests (often demonstrate normal gland functions). Technetium scanning confirms the presence of ectopic thyroid tissue at the base of tongue. There was no normal thyroid gland on scintigraphic and radiological examinations in our case. Histologically; on FNA, LT resembles normal thyroid tissue.
Unless emergency surgery is indicated, suppressive therapy with exogenous thyroid hormone should be tried first in order to decrease the size of the gland. This was the case in our patient and elective surgery following the suppression therapy was planned. Additionally, levothyroxine therapy should be initiated after surgical excision as the lingual thyroid is the only functioning thyroid tissue found in 70% of these patients.11
Lingual thyroid is a rare anomaly representing faulty migration of normal thyroid gland. The exact pathogenesis of this ectopic is not known. It is 7 times higher in females.10
Dysphagia and dysphonia are common presenting symptoms.8 Thorough head and neck examination with special attention to base of tongue is essential. Investigation include thyroid function tests, neck ultrasound scan, Technetium scanning and C.T scan. FNAC is not preferred by some authors as it would cause unnecessary bleeding.7 Although different types of surgical access have been described, the transoral approach provides good exposure and is less traumatic for the patient, with better postoperative recovery.5
The authors declare that they have no conflict of interests.
It is a genuine case report, we accept the final copy and that we accept the journal terms and conditions.
B.A. and S.M. were responsible for the ongoing care of the patient research and drafting the manuscript. All authors read and approved the final manuscript.