Description

• Cyst composed of epithelial remnants of the thyroglossal tract as it descends from foramen cecum at tongue base to the lower neck
• Midline neck mass at the level of the thyrohyoid membrane, closely associated with the hyoid bone, within 2 cm of the midline
• Often asymptomatic midline neck mass but can become infected and rapidly increase in size
• Majority are located between thyroid and hyoid, followed by suprahyoid and then suprasternal, and finally intralingual being the rarest location.
• System(s) affected: endocrine; metabolic; skin; exocrine

Epidemiology

Most common form of congenital midline cyst in the neck, yet rare to present clinically in neonatal period

Incidence

• Majority of cases present in patients <30 years old.
• Predominant sex: male = female

Prevalence
Occurs in up to 7% of population

Etiology and Pathophysiology

• Cystic expansion of a remnant of the thyroglossal duct tract
• Incomplete closure of the thyroglossal duct during gestation
• Persistence of the epithelial tract, the thyroglossal duct, during the descent of the thyroid from the foramen cecum to its final position in the anterior neck
• The thyroglossal duct tract usually atrophies and disappears by the 8th to 10th week of gestation.
• Portions of the tract and remnants of thyroid tissue associated with it may persist at any point between the tongue and the thyroid.
• Failure of the thyroglossal duct to atrophy and involute after descent of the thyroid in the 4th to 7th week of gestation
• Hypothesis: lymphoid tissue associated with the tract hypertrophies at the time of a regional infection, thereby occluding the tract with resulting cyst formation

Genetics

• Usually sporadic; if familial, autosomal dominant is most common mode of inheritance.
• Familial occurrence is extremely rare.

Commonly Associated Conditions

• History of a recent upper respiratory tract infection (URI)
• Ectopic thyroid tissue found in almost half of cysts and rarely associated with ectopic thyroid gland
• Thyroid carcinoma (rare)