Morphological, diagnostic and surgical features of ectopic thyroid gland: A review of literature

Abstract

Ectopic thyroid tissue remains a rare developmental abnormality involving defective or aberrant embryogenesis of the thyroid gland during its passage from the floor of the primitive foregut to its usual final position in pre-tracheal region of the neck. Its specific prevalence accounts about 1 case per 100.000-300.000 persons and one in 4.000-8.000 patients with thyroid disease show this condition. The cause of this defect is not fully known. Despite genetic factors have been associated with thyroid gland morphogenesis and differentiation, just recently some mutation has been associated with human thyroid ectopy. Lingual region in the most common site of thyroid ectopy but ectopic thyroid tissue were found in other head and neck locations. Nevertheless, aberrant ectopic thyroid tissue has been found in other places distant from the neck region. Ectopic tissue is affected by different pathological changes that occur in the normal eutopic thyroid. Patients may present insidiously or as an emergency. Diagnostic management of thyroid ectopy is performed by radionuclide thyroid imaging, ultrasonography, CT scan, MRI, biopsy and thyroid function tests. Asymptomatic euthyroid patients with ectopic thyroid do not usually require therapy but are kept under observation. For those with symptoms, treatment depends on size of the gland, nature of symptoms, thyroid function status and histological findings. Surgical excision is often required as treatment for this condition.

Hürthle Cell Carcinoma in a Lingual Thyroid

“…Children tend to have stunted growth and hypothyroidism. Ultrasonography shows an absent thyroid gland in the laryngeal area in 70% of cases [2]. CT scan or MRI is indicated in the case of lingual thyroid presenting with dysphagia or respiratory obstruction, otherwise a thyroid scan shows lingual thyroid.…”

“…However, during foetal growth, it may fail to descend or may remain close to its original location at the foramen caecum; in rare cases this may result in the development of a lingual thyroid [1]. The normal thyroid gland in the pretracheal area is absent in about 70% cases of lingual thyroid [1,2]. Other sites of ectopic thyroid include submandibular, thyroglossal duct, intra-tracheal, branchial cyst, lung, mediastinal, heart, ovaries, intestine, pancreas, and adrenal glands [1].…”

Differentiated thyroid carcinoma in lingual thyroid

“…However, the reported prevalence of this dysembriogenetic defect increases to 1:4000-8000 when patients with known thyroid diseases are considered [11]. Also, the presence of thyroid-like inclusions was found at histological examination of cadaver tongues in almost 10 % of the examined specimens, with no significant differences in sex distribution [12].…”

“…In 70 % of cases, the LT is the only functionally active thyroid tissue and most patients display mild thyroid insufficiency [5], which often becomes clinically manifest during periods of physiological increased demand of thyroid hormone. In accordance, although symptoms may occur at any age, most LT cases are detected during puberty and pregnancy [11,13,14]. Symptoms are mostly related to the growth of the lingual mass, and include sensation of foreign body, dysphagia, dysphonia, cough, snoring, and, in more severe cases, respiratory obstruction and bleeding [2].…”

Ektopia tarczycy — wyzwania diagnostyczne i terapeutyczne przed wprowadzeniem przesiewowego badania TSH noworodków i po nim

“…The prevalence of ectopic thyroid is estimated at the level of 1 per 100,000-300,000 in the population [1], and 1 per 2500-8000 patients with thyroid disease [5,6]. In another study, the populational incidence of a lingual thyroid was estimated at 1 per 3000-10,000 [7].…”