Oral cavity & oropharynx
Developmental anomalies
Lingual thyroid
Author: Andrey Bychkov, M.D., Ph.D.
Last author update: 1 February 2016
Last staff update: 27 October 2023
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Lingual thyroid
See also: Ectopic thyroid tissue
Table of Contents
Definition / general | Epidemiology | Sites | Pathophysiology / etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Radiology images | Prognostic factors | Case reports | Treatment | Clinical images | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Cytology description | Cytology images | Positive stains | Molecular / cytogenetics description | Videos | Differential diagnosisCite this page: Bychkov A. Lingual thyroid. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/oralcavitylingualthyroid.html. Accessed April 19th, 2024.
Definition / general
- Developmental anomaly in which ectopic thyroid gland is located at the base of tongue
- Tongue is the most common site for total thyroid ectopia
- First reported by Hickman in 1869 (AMA Arch Otolaryngol 1953;57:60)
Epidemiology
- Prevalence in general population is 1 per 10,000 - 100,000 people (Endocr Pract 2016;22:343)
- Historically, thyroid tissue has been found in the tongue in 10% of autopsies (J Pathol 1970;102:239, Oral Surg Oral Med Oral Pathol 1972;34:781)
- F:M = 3 - 7:1
- Mean age at presentation is about 40 years, ranging from infancy to 83 years (Eur J Endocrinol 2011;165:375)
- Some studies report a bimodal age distribution, with peaks in 2nd and 4th decades (Br J Surg 1979;66:537)
Sites
- Most cases arise superficially or submucosally along the midline of base of the tongue between foramen cecum and epiglottis
- Sublingual types (body of the tongue) are rarer and may be suprahyoid, infrahyoid or at the level of the hyoid bone
Pathophysiology / etiology
- Failure of thyroid gland to descend from the foramen cecum to its normal prelaryngeal location
- Pathogenesis is unclear, but there are speculations that maternal antithyroid immunoglobulin may stop thyroid gland descent (Barnes: Surgical Pathology of the Head and Neck, 3rd Edition, 2008)
- Hypothyroidism is commonly seen in patients with lingual thyroid and some have hypothesized that lingual thyroid is a hyperplastic physiologic response by small thyroid remnants in the tongue to a low thyroid hormone level
- Mutation in the genes of thyroid specific transcription factors TTF1, TTF2 (FOXE1) and PAX8 might be involved in thyroid arrest in tongue, as was shown in animals (Nat Genet 1998;19:395); however, no mutation in known genes has so far been associated with the human ectopic thyroid
Clinical features
- Most lingual thyroids are asymptomatic
- Symptomatic lingual ectopia is often manifested in women during puberty, pregnancy or menstruation
- Most common symptoms are dysphagia, dyspnea and upper airway obstruction; other symptoms are foreign body sensation, pain, hemoptysis, dysphonia, snoring and sleep apnea (Endocr Pract 2016;22:343)
- In more than 75% of patients, orthotopic thyroid is absent (total migration failure) and lingual thyroid represents the only thyroid tissue; as a result, 70% of patients with symptomatic lingual thyroid are hypothyroid; hyperthyroidism is exceptionally rare (Int J Surg 2014;12:S3)
- Malignant neoplasms may arise in up to 1% of lingual thyroids; 50+ cases have been reported (J Clin Endocrinol Metab 2011;96:2684)
- Most are follicular carcinomas
- However, recent reports more often encounter papillary carcinomas, which probably reflects greater recognition of the follicular variant of papillary carcinoma (Nikiforov: Diagnostic Pathology and Molecular Genetics of the Thyroid, 2nd Edition, 2012)
Diagnosis
- Radionuclide scan with technetium or radioiodine
- CT, MRI and angiography are important for the preoperative assessment of patients
- FNA helps to differentiate benign from neoplastic conditions
- Incisional biopsy is discouraged due to risk of complications, e.g. infection, necrosis or hemorrhage (Wenig: Atlas of Head and Neck Pathology, 3rd Edition, 2015)
Laboratory
- Hypothyroidism (low T3 and T4, high TSH)
Radiology description
- MRI is useful in estimating extent of a lesion, because it can clearly distinguish thyroid tissue (low-intermediate T2 signal) from the tongue muscle (Hormones (Athens) 2011;10:261)
Radiology images
Images hosted on other servers:
CT and laryngoscopy
SPECT / CT
CT scan:
Distinct margins
Lingual thyroid
Well defined mass
Aberrant thyroid tissue
48-year-old white female with obstructive lingual thyroid
MRI:
Axial MRI: lingual thyroid
38 year old female
Radionuclide scan:
Scintigraphy with Tc-99m
Tc99m pertechnetate planar image
99mTcO4 radionuclide thyroid scan
Thyroid scintigraphy
Angiography:
External carotid artery angiogram
Ectopic thyroid
Carotid arteriography
Prognostic factors
- Prognosis is good, since resection of lingual thyroid achieves significant improvement in patient symptoms with low rates of recurrence (Wenig: Atlas of Head and Neck Pathology, 3rd Edition, 2015)
Case reports
- 7 year old girl with Hashimoto thyroiditis in lingual thyroid (BMJ Case Rep 2013;2013:bcr2013200247)
- 12 year old girl with ectopic lingual thyroid (Case Rep Pediatr 2015;2015:252357)
- 12 year old boy with hyperfuctioning lingual thyroid (J Anaesthesiol Clin Pharmacol 2013;29:132)
- 15 year old girl with lingual thyroid and TSH secreting pituitary adenoma (Case Rep Endocrinol 2013;2013:570847)
- 24 year old woman with follicular adenoma of sublingual ectopic thyroid gland (J Med Case Rep 2014;8:270)
- 25 year old woman with fine needle aspiration diagnosis of hyperfunctioning ectopic thyroid (Acta Cytol 2005;49:228)
- 26 year old man with hemoptysis caused by ectopic lingual thyroid (Quant Imaging Med Surg 2015;5:480)
- 31 year old man with ectopic lingual goiter (Acta Otorhinolaryngol Ital 2013;33:343)
- 40 year old woman with lingual thyroid (Ann Maxillofac Surg 2015;5:104)
- 45 year old woman with dyspnea caused by lingual thyroid (N Engl J Med 2012;366:e15)
- 60 year old man with ectopic lingual thyroid with a multinodular goiter (Surgery 2013;153:294)
- 63 year old woman with differentiated thyroid carcinoma in lingual thyroid (Endocrine 2016;51:189)
Treatment
- Small lesions without symptoms usually require no therapy
- Nonsurgical treatment includes thyroid hormone and radioiodine ablation to induce tissue regression (Int J Surg 2014;12:S3)
- Major indications for surgical excision are airway obstruction and repeated significant hemorrhage
- Transoral robotic surgery (TORS) is the most advanced surgical technique (Thyroid 2013;23:466)
- Most patients with lingual thyroid have no other thyroid tissue and acute hypothyroidism may occur after surgical removal
- Autotransplantation of pieces of lingual thyroid into the neck soft tissues may be considered
Clinical images
Images hosted on other servers:
Tongue mass:
Endoscopy:
Flexible and rigid
Swelling
Lingual thyroid in surgery:
Exposed tumor
Intraoperative photograph and surgical specimen
Gross description
- Midline of base of tongue, usually between circumvallate papillae and epiglottis
- Dome shaped, soft to firm mass with smooth surface, rarely ulcerated
- Several mm to several cm in size (mean 2 - 3 cm)
- Red, smooth to lobulated to nodular, either well or ill defined on sectioning
Gross images
Images hosted on other servers:
Excised specimen
Microscopic (histologic) description
- Thyroid tissue appears normal, with normofollicular and microfollicular patterns
- Follicular cells are benign in appearance, without nuclear features of papillary carcinoma
- Thyroid tissue usually grows between skeletal muscle and minor salivary glands of tongue, which may simulate tumor invasion
- Circumscribed and encapsulated arrangement is rare
- Diagnosis of primary thyroid carcinoma in a lingual site requires vascular invasion, unequivocal infiltration with desmoplastic response or metastasis in the absence of another primary site (Endocr Pathol 2002;13:353)
Microscopic (histologic) images
Contributed by Andrey Bychkov, M.D., Ph.D. and AFIP
Enlarged thyroid follicles
Resembles malignancy
Images hosted on other servers:
With skeletal muscle
Thyroid follicles
Papillary thyroid
carcinoma in
lingual thyroid
Virtual slides
Images hosted on other servers:
Lingual thyroid with follicular carcinoma
Cytology description
- Clusters of follicular cells and colloid, with usual hemorrhagic background (Acta Cytol 2005;49:228)
- Features of associated pathological conditions, e.g. inflammatory and neoplastic, if such are present (Cytopathology 2013;24:275)
Cytology images
Images hosted on other servers:
Follicular cells
Positive stains
- Immunophenotype of thyroid tissue: thyroglobulin, TTF1 in follicular cells and calcitonin in C cells (J Clin Endocrinol Metab 2012;97:951)
Molecular / cytogenetics description
- Mutations typical for thyroid cancer (BRAF V600E, NRAS, HRAS, KRAS) are absent in benign appearing ectopic thyroid tissue (Int J Surg Pathol 2015;23:170)
Videos
Ectopic thyroid in a 6 year old child
Differential diagnosis
- Lingual thyroglossal duct cyst
- Lymphoepithelial cyst of oral cavity
- Some tumors in oral cavity may mimic papillary thyroid carcinoma (Wenig: Atlas of Head and Neck Pathology, 3rd Edition, 2015)
- Cribriform adenocarcinoma of minor salivary glands of oral cavity: thyroglobulin-, TTF1-
- Low grade nasopharyngeal papillary adenocarcinoma: thyroglobulin-, TTF1+
