CASE 12980 Published on 02.04.2016

Dual ectopy thyroid - a case report

Section

Head & neck imaging

Case Type

Clinical Cases

Authors

Dr. Bhanupriya Singh1, Dr. Suhas S. Ghule2, Dr. Dilip L. Lakhkar3, Dr. Sushil Kachewar4

(1) MBBS, MD-Radiodiagnosis II year Resident
(2) MD, DNB, Associate Professor, Radiodiagnosis
(3) Professor & Head, Radiodiagnosis
(4) Professor, Radiodiagnosis

Padmashree Dr. Vitthalrao
Vikhe Patil Hospital;
Post M.I.D.C.
Vadagaon, Vilad Ghat
414111 Ahmednagar;
Email: singh.bhanupriya@outlook.com
Patient

7 years, female

Categories
Area of Interest Ear / Nose / Throat ; Imaging Technique Ultrasound, Ultrasound-Colour Doppler, CT-Angiography, CT, CT-High Resolution
Clinical History
A 7-year-old girl presented to the Department of Paediatrics with a history of difficulty in swallowing and gradually increasing mid-line neck swelling. On examination, two more similar swellings were noted which moved with deglutition and protrusion of the tongue. Swellings were firm in consistency and not hot on palpation.
Imaging Findings
Ultrasonography (USG) and Contrast enhanced Computed Tomography (CE-CT) show a normal right lobe of thyroid (Fig. 1) with empty left thyroid bed (Figs. 2, 3).
USG: Neck swellings were uniformly hyperechoic compared with sternomastoid; with the same echogenicity as thyroid (Figs. 4, 6, 8), showing normal vascularity on Doppler (Figs. 5, 7, 9).
Unenhanced Computed Tomography (CT): The left thyroid lobe is not seen in the expected position. Well-defined focal small hyperdense mass in the left sub-lingual region (Fig. 10). Second well-defined similar mass in the mid-line anterior to the oropharynx at the base of the tongue (Fig. 12). Third lesion noted in the infra-hyoid, pre-laryngeal region (Fig. 14).
CE-CT: ectopic thyroid tissues appear as well-circumscribed homogeneous moderately enhancing masses (Figs. 11, 13, 15)
Sagittal (Fig. 16) and coronal (Figs. 17, 18) reformatted images confirm above specified anatomical location of respective masses.
Conclusion: Orthotopic right lobe of thyroid with three foci of ectopic thyroid tissue, suggestive of a rare phenomenon called "dual ectopy".
Discussion
Ectopic thyroid is tissue not located antero-laterally to the second to fourth tracheal cartilages [1]. In our case the right lobe appears normal (Fig. 1), with an empty left thyroid fossa (Figs. 2, 3).
The thyroid anlage appears in the embryo as a midline structure at the foramen caecum of the tongue. From here, it descends in the midline to reach its final position in the mid-neck [2, 3].
Ectopic thyroid tissue can be found within thyroglossal duct cysts, or anywhere along the course of the thyroglossal duct. Common sites include: foramen caecum (near embryological origin), base of the tongue, anterior tongue, submandibular region, larynx, intra-tracheal, intra-thoracic (mediastinum, heart, lung). [5].
Typically, ectopic thyroid presents as a painless midline neck swelling and can cause dysphagia, inspiratory dyspnoea and stomatolalia due to mass effect. It may coexist with eutopic thyroid or may be the only functioning tissue (in which case it must be preserved) [4].
Any pathology of the thyroid gland can involve ectopic tissue, including benign and malignant conditions.
Indirect clues for confirmation are: separate blood supply of the ectopic gland from extra-cervical vessels, no prior history of malignancy, and normal or absent orthotopic thyroid with no history of surgery [4].
Dual ectopy is a very uncommon condition in which two or more ectopic foci are present simultaneously.
In our case, the first mass is left sublingual (Figs. 4, 5, 10, 11), the second is mid-line, anterior to oropharynx (Figs. 6, 7, 12, 13), and the third is infra-hyoid, pre-laryngeal (Figs. 8, 9, 14, 15) in location. Sagittal (Fig.16) and coronal (Figs. 17, 18) reformatted images confirm above findings.
Sonography shows all three ectopic swellings have the same echogenicity as thyroid (Figs. 4, 6, 8), with normal vascularity on Doppler (Figs. 5, 7, 9).
CT shows mildly increased attenuation (around 110HU) due to intrinsic iodine content (Figs. 10, 12, 14) and homogeneous moderate contrast enhancement (Figs. 11, 13, 15) showing around 150HU attenuation.
Imaging delineates the extension and location of ectopic thyroid tissue, thus contributing to a better pre-surgical evaluation of these cases [5].

Other than lacking the characteristic bilobate shape, ectopic thyroid tissue appears identical to orthotopic thyroid tissue [1].
Asymptomatic euthyroid patients should be followed up.
Patients with high blood TSH levels and swelling should get replacement therapy, which can produce a slow reduction in size.
Obstructive symptoms due to mass effect require surgical intervention [4].
Differential Diagnosis List
Dual ectopic thyroid with orthotopic right lobe
Thyroglossal duct cysts without thyroid tissue
Lymphangioma
Minor salivary gland tumours
Midline branchial cysts
Epidermal and sebaceous cysts
Haemangioma
Adenoma
Fibroma
Lipoma
Final Diagnosis
Dual ectopic thyroid with orthotopic right lobe
Case information
URL: https://www.eurorad.org/case/12980
DOI: 10.1594/EURORAD/CASE.12980
ISSN: 1563-4086