|Year : 2014 | Volume
| Issue : 2 | Page : 238-240
A rare case of triple thyroid ectopia
Mukund Rahalkar1, Anand Rahalkar1, Shrikant Solav2
1 Sahyadri Speciality Hospital, Pune, Maharashtra, India
2 SPECT Lab, Erandawane, Pune, Maharashtra, India
|Date of Web Publication||19-Mar-2014|
721/2B, Navi Peth, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Various anomalies of thyro-glossal duct have been described, in which the duct may form a cyst or may present as a solid nodule to form an ectopic gland. The ectopic gland can develop along the tract of the duct to give rise to ectopic lingual, sublingual (pre-hyoid) or sub-hyoid (pyramidal) gland, with or without normal pre-tracheal thyroid gland.There are a few reports of double ectopia of thyroid but triple ectopia of thyroid is extremely rare. We have come across a case of triple thyroid ectopia, i.e., thyroid tissue at three locations along the tract of descent of thyro-glossal duct on CT, which hast been rarely reported in the world literature, and hence this report.
Keywords: Computed tomography of thyroid anomalies, thyroglossal duct, thyroid ectopia
|How to cite this article:|
Rahalkar M, Rahalkar A, Solav S. A rare case of triple thyroid ectopia. Indian J Endocr Metab 2014;18:238-40
| Introduction|| |
There are many anomalies of development of thyroid gland, which include ectopia along the path of descent of thyro-glossal duct or at other places in the neck.
We have come across triple thyroid ectopia, i.e., nodules of thyroid tissue at three places, namely base of tongue, sublingual or pre-hyoid region and pyramidal lobe. The literature regarding ectopia of thyroid is discussed in the light of CT and isotope study.
The thyroid gland is the first endocrine gland to develop by 24 th day of gestation.
It develops from an endodermal thickening of cells that originate from 3 rd to 4 th branchial pouches. In craniofacial development, the cells move to the base of the tongue to a point known as the foramen caecum. This is where the main anlage of the thyroid develops. From the base of the tongue, the anlage descends from the foramen caecum as the thyroid diverticulum, called as thyroglossal duct, passing anteriorly to the hyoid bone and thyroid cartilage. It settles as a bilobed organ just inferior to the thyroid cartilage, one lobe on each side of the trachea anterolaterally. The two lobes are joined by an isthmus which unites the lobes over the trachea, anterior to the second and third tracheal rings.
The prevalence of ectopic thyroid tissue ranges between 7 and 10%. Lingual thyroid is the most common ectopic thyroid accounting for 90% of all cases with prevalence between 1:100000 and 1:300000 and a clinical incidence between 1:4000 and 1:10000. Other sites of ectopic thyroid are suprahyoid and infrahyoid, lateral aberrant thyroid, substernal goiters, struma ovarii, and struma cordis. Ectopic thyroid has also been found in larynx, trachea, esophagus, pericardium, diaphragm, and branchial cysts. Rare cases of ectopic thyroid are described in parathyroid, cervical lymph nodes, submandibular gland, duodenal mesentery, adrenals, and carotid bifurcation. 
| Case Report|| |
A 42-year-old woman was examined by CT as a client of health check-up to study neck and brain vessels. Her history revealed that she was investigated and counseled by a physician for a nodule over the midline in the neck a few years ago. She was subjected to thyroid function tests, which were normal and excluded hypo or hyper thyroidism. She was correctly advised not to do any further investigation, worry about it or get rid of it surgically.
CT revealed etopic thyroid nodules over the surface of posterior tongue, anterosuperior and close to body of hyoid bone and in sub-hyoid region as an enlarged pyramidal lobe. The normal thyroid lobes and isthmus were absent and as a result common carotid and internal jugular veins were closely applied to trachea without the interposing thyroid lobes [Figure 1]. All these were un-connected and separated by 5-8 mms in craniocaudal direction in the midline. These were hyperdense and showed enhancement (post contrast CT value measuring more than 200. A nuclear scan was performed using 3 millicuries of Technetium 99 m pertechnetate administered intravenously. The static images were acquired at 20 minutes. The frontal projection showed two hot spots, a smaller and upper one between submandibular glands due to lingual ectopia and the lower larger one due to combined activity from pre-hyoid (sublingual) and pyramidal ectopic gland [Figure 2].
|Figure 1: Post contrast axial images showing three hyperdense, (a) enhancing nodules over the surface of posterior tongue measuring 9 × 12 mms in size. (b) second ectopic nodule at a lower level just anterosuperior to the body of hyoid bone measuring 11 × 9 mms in size (c) the third nodule below the hyoid bone and anterior to thyroid cartilage as an enlarged pyramidal lobe measuring 19 × 24 mms in size. (d) an axial image showing absent lateral lobes of thyroid with the result that carotid and jugular vessels are closely applied to trachea|
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|Figure 2: Left half of the image is a sagittal MPR image revealing triple ectopia in a single image. All ectopic nodules are separated by a few mms. The lingual nodule is just behind a small depression or sulcus and is partly buried in the tongue. Right half of the image is a frontal isotope scan shows two hot spots or areas of uptake. The upper one is between submandibular glands and in the midline typically corresponding to lingual ectopia. The lower and larger uptake is due to combined pre-hyoid gland and enlarged pyramidal lobe|
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As she was now asymptomatic and nuclear scan had ruled out any abnormal thyroid function, repeat thyroid function tests were also not recommended.
| Discussion|| |
The thyroid gland is the first endocrine gland to develop in a foetus by 4 th week. The initial thyroid precursor, called as thyroid premordium, begins as a midline diverticulum or epithelium-lined tubular structure, called as thyroglossal duct. It develops over the base of the tongue in a V shaped sulcus between tuberculum impar and copula. The thyro-glossal duct migrates or descends inferiorly anterior to hyoid bone and then to normal pre-tracheal location of thyroid in the neck by 7 th week and disappears by 10 th week. Most of the thyroid gland is derived from this median anlage, while two lateral anlages derived from the 4 th pharyngeal pouch contribute up to 30% of the thyroid tissue.  The most caudal end of thyroglossal duct gives rise to a pyramidal lobe, which may occur in about 30% of individuals. When present it is a very small tubular lobe above the isthmus.
Very rarely further downward or excessive descent may occur outside the tract of thyroglossal duct or embryonic rests may occur in lateral neck, walls of trachea/larynx/esophagus, mediastinum, ovary, pericardium, aortic valve, parotid gland, abdomen, branchial cyst, submandibular gland or adrenal gland.
Remnants of thyroid tissue may develop into ectopic thyroid anywhere along the path of thyro-glossal duct like lingual (over the surface of tongue), sublingual (pre-hyoid) or sub-hyoid (pyramidal lobe) regions.
Genetic research has shown that the gene transcription factors TITF-1(Nkx 2-1), Foxe1 (TITF-2) and PAX-8 are essential for thyroid morphogenesis and differentiation. Mutation in these genes may be involved in abnormal migration of the thyroid. 
Ectopia of thyroid at lingual, sublingual (pre-hyoid) or sub-hyoid location can be with normal or absent pre-tracheal gland. In 70% of cases of lingual thyroid the cervical thyroid is absent. In our case too normal thyroid lobes were absent.
Occasionally there may be dual thyroid ectopia confirmed by CT as well as a nuclear scan, which has been reported in a few articles. , The dual ectopia was lingual and pre-hyoid in one case, while pre- and sub-hyoid in another. In both cases cervical thyroid was absent. Al-Akeely  claimed that there were only eight cases of dual ectopia reported till 2002.
Review of literature reveals that only two cases of triple ectopia have been reported.
Barai,  demonstrated triple ectopia in a hypothyroid child in frontal and lateral nuclear scans. However, no exact anatomical correlation was possible, as CT was not performed. Jain and Pathak,  have also reported a case of triple ectopia of thyroid.
Our case is the third and exceptional case of triple thyroid ectopia with well-defined thyroid nodules seen on CT and further investigated by nuclear scan to be present over tongue and in pre-hyoid and sub-hyoid (pyramidal lobe) locations.
| References|| |
|1.||Kumar Choudhury B, Kaimal Saikia U, Sarma D, Saikia M, Dutta Choudhury S, Barua S, et al. Dual ectopic thyroid with normally located thyroid: A case report. J Thyroid Res 2011;2011:159703. |
|2.||Choi JY, Kim JH. A case of an ectopic thyroid gland at the lateral neck masquerading as a metastatic papillary thyroid carcinoma. J Korean Med Sci 2008;23:548-50. |
|3.||Ibrahim NA, Fadeyibi IO. Ectopic thyroid: Etiology, pathology and management. Hormones (Athens) 2011;10:261-9. |
|4.||Baik SH, Choi JH, Lee HM. Dual ectopic thyroid. Eur Arch Otorhinolaryngol 2002;259:105-7. |
|5.||AL-Akeely MH. Dual thyroid ectopia. Saudi Med J 2003;24:1021-3. |
|6.||Barai S, Bandopadhayaya GP, Kumar R, Malhotra A, Halanaik D. Multiple ectopic thyroid masses in a hypothyroid child. Pediatr Radiol 2004;34:584. |
|7.||Jain A, Pathak S. Rare developmental abnormalities of thyroid gland, especially multiple ectopia: A review and our experience. Indian J Nucl Med 2010;25:143-6. |
[Figure 1], [Figure 2]