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ORIGINAL CONTRIBUTION - CLINICS IN NUCLEAR MEDICINE
Year : 2017  |  Volume : 4  |  Issue : 3  |  Page : 149-153

99mTc-Pertechnetate Scintigraphy in Thyroid Gland Ectopia: Evolving a New Clinical Algorithm


Department of Nuclear Medicine, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India

Date of Web Publication30-Jan-2018

Correspondence Address:
Ravinder S Sethi
Department of Nuclear Medicine, H-Block, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/astrocyte.astrocyte_28_17

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  Abstract 


Introduction: Dual ectopic thyroid has been regarded as a rare developmental anomaly with the most common site being lingual/sublingual and the mode of presentation being hypothyroidism. Patients and Methods: Three patients suffering from dual ectopic thyroid are discussed here along with a review of Indian literature. Conclusion: Increasing reports of dual ectopic thyroid in the literature indicate that the entity might not be so uncommon. Since this is liable to influence the clinical management, especially from the surgical standpoint, thyroid scintigraphy must be included in the preoperative protocol in all cases of thyroid gland ectopia.

Keywords: Dual ectopic thyroid, ectopic thyroid tissue, Indian population, lingual, sublingual, thyroid scintigraphy


How to cite this article:
Das KJ, Sethi RS, Namgyal PA, Sehgal AK. 99mTc-Pertechnetate Scintigraphy in Thyroid Gland Ectopia: Evolving a New Clinical Algorithm. Astrocyte 2017;4:149-53

How to cite this URL:
Das KJ, Sethi RS, Namgyal PA, Sehgal AK. 99mTc-Pertechnetate Scintigraphy in Thyroid Gland Ectopia: Evolving a New Clinical Algorithm. Astrocyte [serial online] 2017 [cited 2018 Oct 16];4:149-53. Available from: http://www.astrocyte.in/text.asp?2017/4/3/149/224193




  Introduction Top


Ectopic thyroid is an uncommon developmental anomaly. The term ectopic thyroid tissue (ETT) refers to any thyroidal mass located distinctly away from its normal pretracheal region. ETT may occur anywhere along the path due to arrest in the descent of the thyroid. Majority of ectopic thyroids are lingual thyroids (90%),[1] sublingual, subhyoid, and suprahyoid.[1] Rare sites reported are higher cervical, intratracheal, mediastinal, and porta hepatitis.[2],[3] The only case of a familial thyroid ectopy has been reported in a mother and son from Japan by Misaki et al.[4]


  Patients and Methods Top


Of all the patients referred to this department for thyroid scintigraphy, three cases of dual ectopic thyroid were detected in a short span of time. The first case was of a 10-year-old male child with a midline swelling in the neck since birth with a clinical suspicion of thyroglossal cyst/ectopic thyroid who was referred for a thyroid scan to locate thyroid gland. Local examination revealed a nontender midline neck swelling soft in consistency and moving with deglutition [Figure 1]a. Oral examination showed another small irregular swelling near the base of the tongue [Figure 1]b. Ultrasonography (USG) revealed a hypoechoic well-defined 2 × 1.7 cm lesion in the neck to the left of the midline with increased vascularity. Thyroid gland was not visualized in orthotopic location. His thyroid profile was T3 = 1.7 (0.69–2.02 nmol/L), T4 = 7.8 (4.4–11.6 μg), and TSH = 15.2 (4–6.2 microIU/ml). Fine needle aspiration cytology (FNAC) from the neck swelling showed colloid goitre with cystic change. Thyroid scintigraphy was performed after intravenous administration of 1.5 mCi 99mTc-pertechnetate. Anterior static images were acquired after 20 min, which revealed a focus of radiotracer concentration in the upper one-third of the neck in midline in the region of clinically palpable swelling in the subhyoid region and another focus of radiotracer concentration in the lingual region, suggesting dual ectopic thyroid [Figure 1]c. No radiotracer uptake was noted in the region of orthotopic thyroid gland.
Figure 1: (a) Ten year male child with midline swelling in neck since birth. (b) Swelling noted at the base of tongue (c) Thyroid scintigraphy (anterior and lateral static images) using 99m-Tc Pertechnetate revealed focus of radiotracer concentration in upper 1/3rdof neck in midline in the region of clinically palpable swelling in the subhyoid region. Another focus of radiotracer concentration was noted in the lingual region suggestive of dual ectopic. No tracer uptake was noted in the region of orthotopic thyroid gland.

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The second case was of an 8-year-old female child who presented with a midline swelling in the neck since 1 year. Local examination revealed a 2 × 2 cm nodule in the midline in upper part of the neck. USG revealed well-defined soft tissue mass measuring 2.5 × 1× 2 cm over thyroid cartilage. Thyroid gland was not visualized in the orthotopic location. Thyroid profile was T3 = 0.5 (0.69–2.02 nmol/L), T4 = 5.0 (4.4–11.6 μg), and TSH = 28.6 (0.4–6.2 uIU/ml). Thyroid scintigraphy performed revealed dual ectopic thyroid tissue with one focus radiotracer concentration in the midline neck in suprahyoid region and another focus in the lingual region [Figure 2]. No radiotracer uptake was noted in the region of orthotopic thyroid gland.
Figure 2: (a) Thyroid scintigraphy revealed two focal area of increased radiotracer uptake in the midline in the suprahyoid region corresponding to the clinically palpable swelling and another focus in the lingual region suggestive of dual ectopic. No tracer uptake was noted in the region of orthotopic thyroid gland. (b) A lateral view of a Tc-99m sodium pertechnetate thyroid scans with chin (short arrow) and angle of mandible (long arrow) markers shows the same findings as in the anterior view.

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The third case was of a 32-year-old female with irregular menstrual bleeding for the last 2 months who was incidentally detected with hypothyroidism in the gynecological outpatient department and referred to the endocrinology department. She was found to have midline neck swelling [Figure 3]. Her thyroid profile revealed T3 = 2.7 (3.5–6.5 pmol/L), T4 = 13.1 (9–20 pmol/ml), TSH = 14.9 (0.4–6.2 mIU/ml), and antiTPO = 73.4 IU/ml. USG abdomen revealed bulky cervix suggestive of cervicitis, whereas her USG neck revealed a well-defined solid lesion measuring 2 × 0.9 cm in the infrahyoid region. Thyroid gland was not seen at the orthotopic position. She was referred to this department to rule out ectopic thyroid gland. Thyroid scintigraphy revealed dual ETT with one focus of radiotracer concentration in the upper one-third of the neck in midline in the subhyoid region and another focus in the sublingual region [Figure 3]a. No radiotracer uptake was noted in the region of orthotopic thyroid gland. Computed tomography (CT) [Figure 3]b and [Figure 3]d and single photon emission computed tomography (SPECT) [Figure 3]c and [Figure 3]e revealed ectopic thyroid tissue on the floor of the mouth in the midline and in the infrahyoid region anterior to the thyroid cartilage.
Figure 3: Thirty two year female with midline swelling in neck. (a) 99m-Tc Pertechnetate scan revealed focus of intense uptake in region of clinically palpable swelling in the subhyoid region. Another focus of radiotracer concentration was noted in the sub-lingual region suggestive of dual ectopic. No tracer uptake was noted in the normal thyroid bed. (b-e) CT and SPECT/CT revealed ectopic thyroid tissue with tracer uptake in midline the floor of mouth and in the subhyoid region anterior to the thyroid cartilage.

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Coming across three cases of dual ectopic thyroid in this department in a short period of time prompted us to review the Indian literature for the same and to find whether this development anomaly is rare or being under reported.


  Discussion Top


Thyroid dysgenesis is usually manifested as ETT, athyreosis, thyroid gland hypoplasia, or hemiagensis.[5] ETT is suspected/diagnosed based on clinical signs and symptoms, FNAC, thyroid function tests, and radiographic imaging studies. Most ectopic thyroid glands are asymptomatic but may manifest at any age, especially during states of increased thyroid hormone demand.[1] Usually, the patients complain of a palpable mass and symptoms depending on its location. Hormone production from ETT is usually insufficient, leading either to a subclinical or clinical hypothyroid state. The incidence of clinical hypothyroidism with ETT varies from 24% to 60%.[6]

Depending on the biochemical profile and symptoms, ETT is treated either with surgery, thyroxine supplement, or 131-Iodine therapy.[7] Thyroxine supplement may be needed in a majority of patients as most patients with ectopic thyroid are hypothyroid. For an asymptomatic euthyroid child, treatment is generally not required, but they must be followed up to look for any complications. If surgery is contemplated, it must be borne in mind that lingual thyroid may be the only functional tissue in 70% of the cases.[8] Therefore, surgery should be reserved for only those cases manifesting with obstructive symptoms, malignancy, or thyrotoxicosis.

On review of the Indian literature it was noted that 32 cases (including the present three cases) of dual ectopic thyroid tissue have been reported in Indian population [Table 1].[6],[7],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28] The mean age at presentation is 12 years (4–32 years), with a female-to-male ratio of 1.9:1. The mean age at presentation, as reported by Chawla et al.,[13] was 18.7 years (4–45 years)with a female-to-male ratio of 1:1. Sood et al.[7] reported a female-to-male ratio of 1.5:1. Therefore, the mean age of presentation of dual ectopic thyroid reported appears to be younger in the Indian population with a higher female preponderance.
Table 1: Literature of dual ectopic thyroid

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Chawla et al.[13] and Sood et al.[7] reported that the most common mode of presentation was euthyroid (48% and 53%, respectively). Gupta et al.[23] reported the same findings. The most common ectopic sites reported were lingual or sublingual followed by subhyoid.[7],[13],[23] In this review, it was noted that the most common mode of presentation in Indian patients was hypothyroid (39.2%), followed by subclinical hypothyroid (35.7%) and euthyroid (25%). The most common sites were either lingual or sublingual (94%), followed by subhyoid (65%) and suprahyoid (31%). No familial thyroid ectopy has been reported in the Indian population so far. In a majority of the cases, orthotopic thyroid gland was absent. Two cases of dual ectopic thyroid were noted in the presence of orthotopic thyroid gland,[11],[18] though in one case, the orthotopic thyroid gland was atrophic [18] and in the other case both the lobes were hypoplastic. One case of dual ectopic thyroid with hemiagenesis of the right lobe [22] has been reported in the Indian literature.

Thyroid USG and scintigraphy are used to image the patients with thyroid dysgenesis. If orthotopic thyroid gland is not seen on USG, then thyroid scintigraphy is required to differentiate athyreosis or ectopia.[29] USG has a sensitivity ranging from 0% to 21% in detecting the ETT,[30],[31],[32],[33] though color Doppler US has higher detection rate.[34] Karakoc-Aydiner et al. showed that USG detected thyroid agenesis in patients by showing absence of detectable thyroid tissue. However, in detecting thyroid ectopia, thyroid scintigraphy demonstrated high sensitivity and specificity compared to USG.[35]

All the three cases reported here presented with neck swelling and were biochemically hypothyroid. All cases had absence of orthotopic thyroid gland on USG. ETT was missed on USG and could only be visualized on thyroid scintigraphy. Thus, these cases and literature review show that lacking in sensitivity and specificity compared to thyroid scintigraphy, routine USG may not be sufficient to diagnose ETT. It might be one of the reasons of fewer reporting of thyroid ectopia. Hence, it is emphasized and an algorithm proposed that in all cases of suspected thyroid ectopia 99m Tc- pertechnetate thyroid scintigraphy with or without SPECT must be included in the preoperative protocol to rule out whether ectopic thyroid tissue is the only functional tissue as it has a bearing on the clinical management of the patient.


  Conclusion Top


Historically, dual ectopic thyroid has been regarded as a rare developmental anomaly. However, increasing reports in the literature indicate that the entity might not be so uncommon. Since this is liable to influence the clinical management, especially from the surgical standpoint, thyroid scintigraphy with or without SPECT/CT must be included in the preoperative protocol in all cases of thyroid gland ectopia. Scintigraphy scores over sonography both in its sensitivity and specificity in identifying such congenital aberrations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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