Abstract
Ectopic thyroid is a condition in which the thyroid tissue is present outside its normal anatomical position. Usually the ectopic thyroid is present along the line of its migration. The presence of ectopic thyroid tissue within the trachea is a very rare condition. Surgery is appropriate treatment for patients with ectopic thyroid tissue with clinical signs of upper airway obstruction. Here we present such a case where an ectopic intratracheal thyroid was causing airway obstruction.
Keywords: Ectopic thyroid, Neck swelling, Airway obstruction
Introduction
The presence of thyroid gland in sites other than its normal pretracheal position is called ectopic thyroid. It occurs due to faulty embryogenesis during its descent from the foramen caecum to its final position. Usually it is located along the site of the thyroglossal duct in which the development of the thyroid gland occurs. About 90% of ectopic thyroid cases are located in the tongue base and approximately 70% of cases with ectopic thyroid do not have a thyroid gland in the normal anatomic localization [1]. Other locations like the heart, lung, duodenum, adrenal gland, gall bladder, porta hepatis, esophagus, parotid salivary gland have been reported [2–6]. When an ectopic thyroid is the only thyroid tissue in the body, removal of such tissue will usually lead to hypothyroidism that requires medical thyroid hormone replacement. This ectopic thyroid tissue does not differ microscopically from that seen in the main thyroid gland [7].
Case Report
A 15 years old female presented with diffuse swelling in front of the neck and difficulty in breathing for 6 years. The swelling was gradually was gradually increasing in size, not associated with pain or hoarseness. She also had difficulty in breathing which was progressive and aggravated on exertion. On examination she had intermittent noisy breathing. The swelling in front of the neck was in midline, butterfly shaped, moved with deglutition and doughy on consistency with no other palpable lymph nodes. Flexible endoscopic examination of the larynx revealed normal mobile vocal cords on both sides and the rest of the larynx and the pharynx was unremarkable. Ultrasonogram of the neck described a picture of multinodular goitre. Fine needle aspiration cytology showed irregularly enlarged follicles, with flattened epithelium without any atypical cells. Within this in hand we had the diagnosis of multinodular goitre. This did not explain the stridor the patient was having. X-ray of the soft tissue of the neck was obtained to evaluate the trachea which showed a soft tissue shadow within the trachea just below the region of the cricoid cartilage. To further define intratracheal mass a contrast enhanced CT scan was done. CT showed a well defined strongly enhancing lesion arising from the posterolateral wall of the trachea causing its significant luminal narrowing and having CT attenuation similar to the thyroid gland (Fig.1). Fat planes with the oesophagus and the left lobe of the thyroid was maintained. Diffuse enlargement of both the lobes of thyroid gland and isthmus without any hypo or hyper enhancing nodule or calcification was also seen (Fig. 2). Thyroid scintigraphy was not included in the investigation because of the stridor and the urgency to maintain the patency of the airway. With this findings the diagnosis of a probable intratracheal ectopic thyroid was made however the possibility of thyroid carcinoma invading the trachea was also considered. A tracheostomy was done below the level of the intratracheal mass under local anesthesia which was immediately followed by a conventional total thyroidectomy. No invasion of the tracheal tissue by the thyroid was noted. After total thyroidectomy, a vertical midline incision was given on the anterior wall of the trachea and the intratracheal mass was visualised. It was separated from its attachment by blunt dissection and removed. Trachea was sutured at the incision site and the skin was closed in layers with a suction drain in situ after achieving haemostasis. Postoperative period was uneventful and the tracheostomy tube was removed on the fifth postoperative day. Histopathology of the thyroid lobes and the isthmus were same as the intratracheal mass. It showed encapsulated thyroid tissue containing varying sized thyroid follicles lined by cuboidal cells and lumen containing eosinophilic colloid. No atypical feature was seen.
Fig. 1.
Lesion causing significant tracheal luminal narrowing
Fig. 2.
Lesion arising from the posterolateral wall of the trachea causing its significant luminal narrowing and having CT attenuation similar to the thyroid gland
Discussion
During embryological development, the thyroid gland migrates down from the foramen caecum at the posterior aspect of the tongue to its permanent location. Abnormality in the migration at any point leads to the thyroid remaining in abnormal position. Ectopic thyroid tissue is mostly seen in women and in the second decade of life [1]. Although about 70% of cases with ectopic thyroid do not have a thyroid gland in the normal anatomic localization this patient present presented with a multinodular goiter of the normal thyroid as well.
The symptoms of ectopic thyroid tissue differ according to its location. Since most of the cases occur in the thyroglossal line, they generally present with dysphagia, dysphonia or asymptomatic neck mass. Intratracheal ectopic thyroid presented with dyspnoea and noisy breathing however it can remain asymptomatic if present in adrenal, duodenum, intestine pancreas and intrathoracic region. The thyroidal status in ectopic thyroid is usually euthyroid or hypothyroid [8].
When ectopic thyroid tissue is suspected, ultrasonography, computed tomography, and magnetic resonance imaging provide valuable findings both for the differential diagnosis and for surgical intervention however thyroid scintigraphy is the golden standard method for the detection of ectopic thyroid tissue [1]. It is very uncommon for two ectopic foci to be present simultaneously. If present, the first lesion is lingual or sublingual and the second is subhyoid, infrahyoid or suprahyoid region in most of the cases [9]. Primary thyroid carcinoma of the ectopic thyroid has also been reported some cases where papillary carcinoma were commonly found [10, 11]. Surgery is appropriate treatment for patients with ectopic thyroid tissue with clinical signs of upper airway obstruction or when the lesion shows features of thyroid malignancy. In cases when a surgical approach cannot be applied, suppressive hormone therapy with levothyroxine in order to avoid ectopic thyroid tissue growth and radioiodine ablation with I-131 for decreasing tumor’s size can be proposed [12].
Conclusion
In conclusion, developmental anomaly during embryogenesis lead to ectopic thyroid tissue, residing anywhere along the gland’s embryological descending pathway, as well as in distant areas. Intratracheal ectopic thyroid along with thyroid in with normal pretracheal position is a very rare entity with the possibility of producing life threatening airway obstruction. Surgery is the treatment of choice in such cases where the airway patency can be effectively maintained by removing the ectopic thyroid tissue.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
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