1. Ectopic Thyroid Gland
Intern 陳君豪
2005/08/22

2. Ectopic Thyroid
The entire thyroid gland can fail to descend to its normal adult site
In approximately 1 in 200,000 normal subjects and 1 in 6,000 patients with thyroid disease

3. Ectopic Thyroid
The most frequent midline cervical masses in the pediatric population are thyroglossal duct cysts (TGDCs)
Avoid the excision of what may be the only source of functioning thyroid tissue

4. Embryology
During the fourth week of gestation, a ventral diverticulum of the foramen caecum is formed from the first and second pharyngeal pouches

5. Embryology
This diverticulum, with its narrow neck connected to the tongue, descends in the midline of the neck as the thyroglossal tract to the position of the normal thyroid

6. Embryology
The tract usually atrophies and disappears by the tenth week of gestation

7. Thyroglossal Duct Cysts
The most common form of congenital cyst in the neck
Cysts of epithelial remnants of the thyroglossal
tract

8. Thyroglossal Duct Cysts

9. Thyroglossal Duct Cysts
Patients with thyroglossal duct cysts often have ectopic thyroid glands
57% had ectopic thyroid tissue among patients with thyroglossal duct cysts

10. Ectopic Thyroid
Prevalence is higher in females than in males, with a female-to-male ratio of 7:1
In approximately 1 in 200,000 normal subjects

11. Ectopic Thyroid
Lingual and sublingual, prelaryngeal, intralaryngeal, intratracheal, submandibular site
Aortic wall, intrathymic, retropharyngeal, intracardiac site, in the esophagus and in the abdomen

12. Ectopic Thyroid
Lingual thyroid: descent is completely arrested at the level of the base of tongue

13. Ectopic Thyroid Sublingual or prelaryngeal position: partial descent
Substernal ectopic gland: excessive migration
Among ectopic thyroid glands, 90% are lingual and 10 percent occur in other sites

14. Parapharyngeal ectopic thyroid

15. Ectopic Thyroid
In patients presenting with a lingual thyroid, over 70 percent have no thyroid tissue in the normal location

16. Symptoms and Signs
Clinically, the majority of patients with thyroid ectopia are asymptomatic, so that the true incidence is unknown
Obstructive symptoms and hypothyroidism have been observed

17. Symptoms and Signs The ectopic tissue is typically found incidentally
though these masses can be symptomatic dyspnea, dysphagia, dysphonia, hemoptysis or hoarseness.

18. Diagnosis - US
Ultrasound can localize and characterize anteromedial neck masses, the presence contour, and size is highly likely to be a normally functioning gland

19. Diagnosis - CT
CT scans often reveal a homogenous hyperdense mass because of the high iodine content
The thyroid gland also enhances because of its vascularity
Not typically recommended in the routine evaluation of pediatric anterior neck masses because of radiation exposure

21. Diagnosis - MRI
Most useful in lingual thyroid cases for situations in which delineation of thyroid tissue from tongue muscle is difficult
Lingual thyroid tissue is hyperintense compared with tongue musculature on both Tl and T2 MRI sequences, and it strongly enhances with contrast injection

22. Diagnosis - MRI MRI offers less radiation exposure than CT
However, disadvantages include increased cost, longer imaging time, and necessitates the use of anesthesia in the pediatric population.

24. Diagnosis - Thyroid Scan
Clinical evidence of hypothyroidism or when ultrasound fails to visualize glandular tissue in the normal position
Assess if the mass is functioning and to determine if this tissue is the only viable thyroid material

25. Diagnosis - Thyroid Scan
Tc 99m sodium is a radio-active tracer that is actively transported into thyroid cells by an iodide pump.
Evaluation of anterior neck masses in children is controversial. Given the comparative rarity of cervical ectopic thyroid, the vast majority of routine preoperative thyroid scans will yield negative results

26. Management
The treatment of ectopic thyroid depends on its location and size and on the presence of symptoms or complications
In cases of small and asymptomatic ectopic thyroid, the functioning thyroid should be kept under observation

27. Management
The mainstay of treatment for ectopic thyroid is hormonal therapy
Thyroid hormone therapy will also typically suppress the production of thyroid stimulating hormone
Clinically symptomatic or cosmetically disturbing cervical glandular enlargement.

28. Management
Progressive hypothyroidism, dysphagia, bleeding, or airway obstruction despite hormonal therapy are indications for surgical excision
Such excision of ectopic thyroid commits the patient to lifelong thyroid hormone replacement

29. Thanks for your attention !!