Thyroglossal duct cyst

• Painless, firm, midline neck mass that elevates with swallowing and tongue protrusion
• Usually located near the hyoid bone
• May cause dysphagia or neck/throat pain
• Pathophysiology
  • The thyroid gland originates from the foramen cecum at the base of the tongue and descends caudally into the neck, forming the thyroglossal duct.
  • If the thyroglossal duct fails to obliterate, midline neck cysts or ectopic thyroid tissue can develop anywhere along its path.

Branchial cleft cyst

• Definition: remnants of the embryological second branchial cleft or cervical sinus, which normally regresses before birth
• Pathophysiology: formed due to incomplete obliteration of branchial clefts and pouches
• Clinical features: usually diagnosed in late childhood or in adulthood after a previously undiagnosed cyst becomes infected
  • History of upper respiratory infection
  • Painless, firm mass
    • Located lateral to the midline, usually anterior to the sternocleidomastoid muscle
    • Does not move with swallowing
  • There may be a small draining opening if a fistula is present.
• Ultrasound: Round mass with uniform low echogenicity and no internal septations

Cystic hygroma

• Definition: a congenital lymphatic cyst (macrocystic lymphangioma) in the posterior triangle of the neck caused by malformation and obstruction of the fetal lymphatic system
• Epidemiology
  • ∼ 1:6,000 live births
  • Strongly associated with fetal aneuploidy (e.g., Turner syndrome, trisomy 21) and congenital malformations (e.g., congenital heart defects)
• Clinical features
  • Present at birth as a soft, compressible, painless, posterior triangle neck mass
  • Can cause dysphagia or airway compromise
  • Positive transillumination test