Description

• Usually midline neck mass at the level of the thyrohyoid membrane, closely associated with the hyoid bone
• Within 2 cm of the midline
• Single, smooth, nontender, and mobile
• 65% infrahyoid type
• 20% suprahyoid
• 15% juxtahyoid
• 10% suprasternal
• Intralaryngeal very rare: Suprasternal notch, superior mediastinum
• Endolaryngeal cyst (ectopic location): Extremely rare
• System(s) affected: Endocrine; Metabolic; Skin; Exocrine

Epidemiology

• Most common form of congenital cyst in the neck
• Accounts for 2–4% of all neck masses

• Most patients are children/adolescents.
• Up to 1/3 are aged ≥20 years.
• Predominant age: 50% <10 years, 65% <20 years
• Predominant sex: Male = Female
• Caucasian race

• Thyroglossal duct cysts were found in 7% of adults in 1 autopsy study.
• Thyroglossal duct anomalies are the 2nd most common pediatric neck mass, behind adenopathy in frequency.

Risk Factors

• Usually sporadic; if familial, autosomal-dominant is most common mode of inheritance (1).
• Familial occurrence is extremely rare (2).

Pathophysiology

• Cystic expansion of a remnant of the thyroglossal duct tract
• 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–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.
• The wall of a thyroglossal duct is the 2nd most common site for ectopic thyroid tissue.

Etiology

• Failure of the thyroglossal duct to atrophy and involute after descent of the thyroid in the 4th–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.

Commonly Associated Conditions

• Often the patient has a history of a recent upper respiratory tract infection.
• Ectopic thyroid tissue is found in 50% of patients.
• If thyroid gland fails to descend to orthotopic site, an ectopic thyroid gland results. Most ectopic thyroid glands are lingual. Many patients with ectopic thyroid gland are hypothyroid.