Thyroid Research and Practice

CASE REPORT
Year
: 2014  |  Volume : 11  |  Issue : 3  |  Page : 113--115

'Two are not always better than one' - Dual Ectopic Thyroid: A rare anomaly


Ashutosh Kansal1, Shruti Aggarwal2,  
1 Department of Pathology, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization, Timarpur, Delhi, India
2 Department of Dermatology, Subham Skin Clinic, Kaushambi, Ghaziabad, Uttar Pradesh, India

Correspondence Address:
Ashutosh Kansal
Department of Pathology, Institute of Nuclear Medicine and Allied Sciences, Defence Research and Development Organization, Brig, S. K. Majumdar Road, Timarpur, Delhi 110 054
India

Abstract

Congenital abnormalities are the least common of the thyroid disorders. It is very unusual for dual ectopic foci of thyroid tissue to be present simultaneously. We are reporting a case of dual ectopic thyroid in the lingual and sub-hyoid areas in a 15-year-old boy with no thyroid gland in its normal anatomical location. However, physical examination showed monoectopic thyroid presented as a 3 × 3.5 cm anterior midline neck swelling just below the hyoid bone, though the neck ultrasonography and thyroid scan with technetium-99m sodium pertechnate confirmed lingual and sub-hyoid dual ectopic thyroid with no thyroid tissue at the normal anatomical location of the thyroid gland.



How to cite this article:
Kansal A, Aggarwal S. 'Two are not always better than one' - Dual Ectopic Thyroid: A rare anomaly.Thyroid Res Pract 2014;11:113-115


How to cite this URL:
Kansal A, Aggarwal S. 'Two are not always better than one' - Dual Ectopic Thyroid: A rare anomaly. Thyroid Res Pract [serial online] 2014 [cited 2021 Dec 7 ];11:113-115
Available from: https://www.thetrp.net/text.asp?2014/11/3/113/138557


Full Text

 INTRODUCTION



Ectopic thyroid is a rare developmental anomaly with a reported prevalence between 1:100000 and 1:300000 and a clinical incidence 1:4000 to 1:10000. [1] It occurs when there is an abnormality in the descent of embryonic median or lateral thyroid anlage, which usually occurs on 3 rd to 7 th week of embryonic life from the posterior dorsal midline of the tongue to its final normal pretracheal location in the lower neck. The location decides the type of the ectopia, namely, lingual (at the base of the tongue), sublingual (below the tongue), prelaryngeal (sub-hyoid) or substernal (mediastinal). The diagnosis is based on the clinical features, fine needle aspiration cytology, laboratory tests and radiographic imaging studies. A careful assessment is required as the lingual thyroid may be the only functioning thyroid in 70% of cases. [2] It is more unusual for two distinct foci of ectopic thyroid tissues to be present simultaneously. Only 30 cases of dual ectopic thyroid so far have been reported in literature, with the majority of them in the midline region of the anterior neck. [3] Herein, we report a case of a 15-year-old boy with dual ectopic thyroid (lingual and sub-hyoid) with hypothyroidism where the diagnosis and its subsequent management were established with the help of ultrasonography (USG) and technetium-99m (Tc-99m) pertechnetate thyroid scan.

 CASE REPORT



A 15-year-old boy presented to our out-patient department with complaints of progressively increasing swelling in the midline of upper neck for last 6 years. He gave history of recent increase in size of the swelling but has no pressure symptoms such as foreign body sensation, dysphagia, dysphonia or dyspnea. He had no complaints suggestive of thyroid functional disorders. On examination, patient had a well-defined, firm swelling of 3 × 3.5 cm located at the sub-hyoid region [Figure 1]. There was no associated cervical lymphadenopathy. His thyroid function tests revealed normal free triiodothyronine (FT3) - 4.99 pmol/L (2.8-7.1 pmol/L) and free thyroxine (FT4) - 13.57 pmol/L (12-22 pmol/L) levels, but elevated thyroid stimulating hormone (TSH) - 35.9 μIU/ml (0.27-4.2 μIU/ml) suggestive of hypothyroidism. USG of the neck revealed presence of sub-hyoid mass [Figure 2]a-c]. However, clinical examination did not reveal any obvious lingual mass at the time of presentation. The fine needle aspiration of sub-hyoid mass revealed abundant thick and thin colloid, normal thyroid follicular cells arranged in sheets and clusters and cyst macrophages. [Figure 3].{Figure 1}{Figure 2}{Figure 3}

Technetium 99m pertechnetate thyroid scan with 2 mCi (74 MBq) showed an absence of trapping of isotope in the normal pre-tracheal position of thyroid and an enhanced uptake in the lingual and sub-hyoid regions, suggestive of dual ectopic thyroid with hypothyroidism and the effect of raised thyroid-stimulating hormone (TSH). [Figure 4]. The patient was treated conservatively with thyroid replacement therapy and followed up with clinical examination for decrease in the size of the swelling and thyroid function tests for achieving euthyroid levels.{Figure 4}

 DISCUSSION



Ectopic thyroid was first described by Hickman in 1869 in a newborn who was suffocated 16 hours after birth because of a lingual thyroid causing upper airway obstruction. [4] Lingual thyroid is the most common ectopic thyroid accounting for 90% of all cases. Other sites of ectopic thyroid are suprahyoid and sub-hyoid, lateral aberrant thyroid, substernal goiters, struma ovary 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. Existence of ectopic thyroid glands at two different locations is very rare with total 30 reported cases and triple ectopic thyroid is even rarer with only two cases having been reported in literature. [3]

The pathogenesis of this condition remains unknown. However, it is postulated that maternal anti-thyroid antibodies may arrest the gland's descent and predispose the patient to poor thyroid function later in life. [5]

Most ectopic thyroid glands are asymptomatic and benign and commonly detected during periods of increased demand for thyroid hormones, e.g., puberty and pregnancy. Increased levels of thyrotropin at these periods causes goitrous enlargement of the ectopic thyroid tissue as in our case and may also be associated with clinically evident thyroid dysfunction, which could be either hypofunction or hyperfunction. [6] Malignant transformation has been reported in 1-3% of cases, and approximately 80% of such tumors are papillary carcinomas. [7]

Radionuclide thyroid imaging employing Technetium-99m pertechnetate, iodine-131 or iodine 123 is useful in the evaluation for ectopic thyroid. Thyroid tissue takes up the radioisotope and this helps in localizing the ectopic thyroid and at the same time in determining the presence of a eutopic thyroid gland. This is crucial to know before surgical removal of the ectopic tissue since in more than half of the patients with thyroid ectopy, no other functioning thyroid tissue exists. [8]

In our case, we suspected the diagnosis based on clinical picture, wherein the patient presented for a cosmetic reason due to midline sub-hyoid swelling with no obstructive or pressure symptoms and thyroid function tests, which showed hypothyroidism (with raised TSH). We did ultrasound of neck, which revealed the absence of thyroid gland in the normal pre-tracheal position and the presence of two midline homogenous masses, one seen at the base of tongue and other over the hyoid bone. These findings were then confirmed using a Technetium-99m scintigraphy of neck, which revealed no uptake of isotope in the normal pre-tracheal region and enhanced uptake in the base of tongue and sub-hyoid region.

Management of ectopic thyroid tissue is dependent on several factors including size of lesion, presence of local symptoms, age and status of thyroid gland and presence of complication factors like ulceration, hemorrhage or malignancy. [10] Options include hormone therapy, radioiodine ablations and surgery. Surgical excision of ectopic thyroid is seldom necessary, but has to be considered in life-threatening airway obstruction, malignancy and thyrotoxicosis. [9] Surgery is deferred in our case and the patient is put on a long-term thyroid replacement with 50 micrograms, once daily and advised for follow up regularly with thyroid function tests.

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