Ectopic thyroid tissue: anatomical, clinical, and surgical implications of a rare entity

Abstract

Ectopic thyroid tissue is a rare entity resulting from developmental defects at early stages of thyroid gland embryogenesis, during its passage from the floor of the primitive foregut to its final pre-tracheal position. It is frequently found around the course of the thyroglossal duct or laterally in the neck, as well as in distant places such as the mediastinum and the subdiaphragmatic organs. Although most cases are asymptomatic, symptoms related to tumor size and its relationship with surrounding tissues may also appear. Any disease affecting the thyroid gland may also involve the ectopic thyroid, including malignancy. The clinician must distinguish between ectopic thyroid and metastatic deposits emerging from an orthotopic gland, as well as other benign or malignant masses. Thyroid scintigraphy plays the most important role in diagnosing ectopy, but ultrasonography contributes as well. In cases of symptomatic disease, surgery is the treatment of choice, followed by radioiodine ablation and levothyroxine suppression therapy in more refractory cases. This review provides current understanding about the wide clinical spectrum of this rare condition, also referring to optimal diagnostic approach, differential diagnosis, and management strategies.

Heterotropic Pulmonary Thyroid in the Presence of a Normally Located Multinodular Goitre

“…While intrapulmonary heterotropic thyroid tissue is rare, cervical, mediastinal and intra-abdominal heterotropic thyroid lesions are more common [4]. Other very rare locations for heterotropic thyroid include the pituitary [5] and the iris [6].…”

Dynamic sonographic examination of an ectopic sublingual goiter

“…1,2 The ectopic thyroid tissue can be found anywhere along the descending pathway of the thyroid gland: in the base of the tongue (lingual), between the geniohyoid and mylohyoid muscles (sublingual, suprahyoid), anterior to the larynx (prelaryngeal), or in the mediastinum. Cases of supradiaphragmatic (intrathoracic) and subdiaphragmatic ectopic thyroid tissue have also been reported.…”

Lingual Papillary Thyroid Carcinoma with Bilateral Neck Node Metastasis

“…1 It descends anterior to the pharyngeal gut leaving only the foramen cecum at the posterior aspect of the tongue. The incidence of ectopic thyroid tissue is 1 in every 100,000 to 300,000 in general population 2 and lingual thyroid (first described by Hickman 3 in 1869) is the most common ectopic site (90%). 4 Lingual thyroid is common in females (80%).…”

“…5 In 70% of the cases, it is the only functioning thyroid tissue. 6 1 Senior Resident, 2 3 Although 99% of thyroid cancers develop within the thyroid, in rare cases, it can arise from the ectopic thyroid tissue. 7 Rarity of this cancer justifies reporting this case.…”

“…8 The number of reported neoplasms occurring in this tissue seems disproportionately small when compared with the frequency of tumor formation in the normally placed thyroid. Noussios et al 2 have written of 15% malignant transformation of the ectopic thyroid.…”