Address for correspondence : Seung Woo Kim, MD, Department of Otolaryngology-Head and Neck Surgery, VHS Medical Center, 53 Jinhwangdo-ro 61-gil, Gangdong-gu, Seoul 134-791, Korea
Tel : +82-2-2225-1384, Fax : +82-2-2225-1385, E-mail : entzzang1020@daum.net

Introduction

Thyroglossal duct cyst (TGDC) and lingual thyroid (LT) are relatively common developmental anomalies of the thyroid gland. The former is the most common congenital malformation in childhood, usually presenting as a midline neck mass.¹⁾ The latter stems from the existence of thyroid tissue at the foramen cecum, presenting as a tongue base mass.²⁾ Each of these can arise without the orthotopic thyroid gland, but the co-existence of all three anomalies is extremely rare. We report a 71- year-old woman with all three of these anomalies. To the best of our knowledge, this is the third report of such a case in the English literature.^1,2)

Case

A 71-year-old woman had been referred to our department for midline neck mass which had persisted from childhood. Prior to the presentation, the patient had been diagnosed with a subclinical hypothyroidism, and had been managed with thyroxine supplement by the endocrinologist at our institution. Physical examination revealed a 3×6 cm, smooth, soft, round and well-margined neck mass that was midline. The mass moved up or down with swallowing or tongue protrusion (Fig. 1). Rigid laryngoscopic exam revealed a soft, pinkish, well-margined and round mass in the tongue base (Fig. 2). Other physical examination was unremarkable, and the patient denied any history of hereditary thyroid disease or radiation exposure. The free T4 and TSH level were 1.01 ng/dL (reference range: 0.8-1.8), 4.82 μIU/mL (reference range: 0.15-4.2) each. The level of anti-thyroglobulin and anti-microsomal antibody was within normal limits. An ultrasonography (US) of the neck revealed a hypoechoic mass with isoechoic mural nodule with an internal macrocalcification. Computerized tomography (CT) revealed a low attenuated density mass with internal calcification in midline neck and a slight enhancing, well-margined mass in the base of tongue. No orthotopic thyroid gland was observed either of these imaging studies (Fig. 3). I-131 whole body scanning revealed dense uptake at the level of tongue base and midline neck. There was no uptake in the normal thyroid position (Fig. 4). The sono-guided fine needle aspiration cytology (FNAC) of the midline neck mass revealed cytologic category II by Bethesda classification. Putting these findings together, we confirmed the diagnosis of TGDC with LT without orthotopic thyroid gland. We considered various clinical factors, such as thyroid function, patient preference, cosmetic problem and age. The patient was informed that the surgery may worsen the symptoms of hypothyroidism, but she strongly wished for surgical removal. Therefore, we performed the classical Sistrunk's operation with the preservation of lingual thyroid. In the operation, the midline neck mass was easily dissected without adhesion. No orthotopic thyroid was identified, but the superior parathyroid gland and recurrent laryngeal nerve were located in the usual anatomic positions (Fig. 5). The final pathologic report was compatible with TGDC and nodular hyperplasia. There was no postoperative complication except aggravated hypothyroidism. She goes to the department of endocrinology regularly, and requires increased dose of thyroxine supplement.

Discussion

A TGDC results from the persistence and dilatation of epithelial tract remnants formed during the embryogenesis of the thyroid gland.²⁾ Developmentally, this duct normally degenerates between 8th and 9th weeks of gestation. Approximately 7% of the population has thyroglossal duct remnants and 50% of such thyroglossal duct contains thyroid tissue.³⁾ In general, the cyst presents as a mass between tongue base and anterior neck. Depending on the location, this anomaly can be classified as; infra-hyoidal (61%), supra-hyoidal (24%), supra-sternal (13%), and intra-lingual (2%).⁴⁾
Preoperative evaluation of TGDC includes thyroid scan, thyroid function test, US and CT. The thyroid scan plays a role in the detection of other ectopic and functioning thyroid tissue.²⁾ The differential diagnosis of TGDC includes epidermoid, dermoid, lipoma and teratoma, and the radiologic studies are essential in this work up.⁵⁾ TGDC is located inside the strap muscle, but epidermoid and dermoid exist outside the muscle.⁶⁾ About 1% of TGDC is combined with malignancy and consists of papillary adenocarcinoma (80%), papillary/follicular mixed (7%) and then squamous type (5%).⁷⁾ A medullary carcinoma with TGDC has not been reported. FNAC must be performed if the mass is fixed, hard or has rapid enlargement with palpable neck node or if the US shows a mural mass with micro-calcifications.⁶⁾ Because of hypo-echogenic nodule and internal calcification in US and CT of our patient, we initially presumed the TGDC with papillary thyroid cancer (PTC). But the FNAC revealed benign cytologic features.
In case of small asymptomatic TGDC with LT, simple observation with periodic sonography is recommended. But, if relative large symptomatic TGDC with cosmetic problem is presented, the treatment choice is the classical Sistrunk's operation with preservation of LT.⁵⁾ In TGDC with PTC, the extent of surgery is determined by the prognostic factors of PTC.⁷⁾ The Sistrunk's operation plus thyroidal isthmectomy or total thyroidectomy with/without central neck dissection is mandatory.^4,7) In our case however, the TGDC had thyroid tissue with nodular hyperplasia, and the extent of resection afforded by Sistrunk's procedure was considered adequate.
According to previously published case series, an ectopic thyroid can be classified as; lingual (23/49), sublingual (17/49), combined (7/49) and intratracheal (1/49).⁸⁾ Among these, only four cases had thyroid tissues in an orthotopic position, and 62% had demonstrated hypothyroidism. In our patient, lingual thyroid did exhibit endocrinal activity, and this may be the only functional thyroid.⁸⁾ Malignant change of LT is much rare when compared to that of TGDC, and the histologic types are well-differentiated or medullary.⁹⁾
The diagnostic work-up for lingual thyroid includes TSH, thyroxine, T3 uptake level and thyroid scan.²⁾ The differential diagnosis includes lingual TGDC, hypertrophic lingual tonsil, hemangioma, lipoma, papilloma, adenomas and fibroma.⁵⁾ The treatment options are suppression therapy with T4, surgical removal and, low dose radioactive iodine ablation, and the choice of treatment depends on thyroid function, aesthetic concern, and patient age and prererences.¹⁾ If the patient is in euthyroid state with orthostatic thyroid, simple observation is recommended. If there is hypothyroidism without orthotopic thyroid, thyroxine medication is mandatory. It is also reported that resected lingual thyroid in symptomatic patient can be auto-transplanted into the lateral pharyngeal wall or mouth floor.^10,11) Thereby, hypothyroidism is relatively well prevented.
Co-existence of these three developmental anomalies (TGDC, LT, absence of orthotopic thyroid gland) are extremely rare, only two reports have been published in English literature (Table 1).^1,2) The combinations of these three anomalies imply the failure of normal descent of the thyroid during gestation.¹⁾ It is reported that the maternal anti-thyroid antibody may have an impact on the process of normal thyroidal development.^1,12)
This case highlights the treatment modalities of TGDC concomitant with LT. We report a very rare and unique disease entity with a literature review.

1. Madana J, Kalaiarasi R, Yolmo D, Gopalakrishnan S. Simultaneous occurrence of a thyroglossal duct cyst and a lingual thyroid in the absence of an orthotopic thyroid gland. J Laryngol Otol 2012;126(2):217-20.

2. McCoul ED, de Vries EJ. Concurrent lingual thyroid and undescended thyroglossal duct thyroid without orthotopic thyroid gland. Laryngoscope 2009;119(10):1937-40.

3. Madana J, Yolmo D, Saxena SK, Gopalakrishnan S. True thyroglossal fistula. Laryngoscope 2009;119(12):2345-7.

4. Plaza CP, López ME, Carrasco CE, Meseguer LM, Perucho Ade L. Management of well-differentiated thyroglossal remnant thyroid carcinoma: time to close the debate? Report of five new cases and proposal of a definitive algorithm for treatment. Ann Surg Oncol 2006;13(5):745-52.

5. Sameer KS, Mohanty S, Correa MM, Das K. Lingual thyroglossal duct cysts--a review. Int J Pediatr Otorhinolaryngol 2012;76(2):165-8.

6. Huoh KC, Durr ML, Meyer AK, Rosbe KW. Comparison of imaging modalities in pediatric thyroglossal duct cysts. Laryngoscope 2012;122(6):1405-8.

7. Choi YM, Kim TY, Song DE, Hong SJ, Jang EK, Jeon MJ, et al. Papillary thyroid carcinoma arising from a thyroglossal duct cyst: a single institution experience. Endocr J 2013;60(5):665-70.

8. Yoon JS, Won KC, Cho IH, Lee JT, Lee HW. Clinical characteristics of ectopic thyroid in Korea. Thyroid 2007;17(11):1117-21.

9. Yaday S, Singh I, Singh J, Aggarwal N. Medullary carcinoma in a lingual thyroid. Singapore Med J 2008;49(3):251-3.

10. Rojananin S, Ungkanont K. Transposition of the lingual thyroid: a new alternative technique. Head Neck 1999;21(5):480-3.

11. Wu ZX, Zheng LW, Dong YJ, Li ZB, Zhang WF, Zhao YF. Modified approach for lingual thyroid transposition: report of two cases. Thyroid 2008;18(4):465-8.

12. Danner C, Bodenner D, Breau R. Lingual thyroid: iodine 131: a viable treatment modality revisited. Am J Otolaryngol 2001;22(4):276-81.