Congenital neck masses

Mass	Location	Pathophysiology	Key Differentiator
Thyroglossal Duct Cyst	Midline	Persistent thyroglossal duct remnant	Moves with swallowing
Branchial Cleft Cyst	Lateral (Ant. to SCM)	Incomplete obliteration of 2nd branchial cleft	Immobile with swallowing
Cystic Hygroma	Posterior Triangle	Malformation of lymphatic system	Transilluminates; Assoc. w/ Turner Syn.
Fibromatosis Colli	Within SCM muscle	Fibrous hyperplasia of SCM	Infantile Torticollis

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

• Peak presentation: Late childhood, adolescence, or early adulthood (often unnoticed until rapid enlargement following an upper respiratory infection [URI]). c

• Clinical features:

  • Location: Lateral neck, characteristically along the anterior border of the sternocleidomastoid (SCM) muscle (near the angle of the mandible).
  • Presentation:
    • Painless, smooth, fluctuant, slow-growing lateral mass.
    • Does NOT move with swallowing or tongue protrusion (crucial negative finding).
    • May present as a tender, enlarged, erythematous mass if secondarily infected.
    • External cutaneous opening or draining fistula/sinus tract may be present.

• Ultrasound: Round mass with uniform low echogenicity and no internal septations

Tip

Branchial cleft cysts manifest as a painless, firm neck mass lateral to the midline.

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
  • Strong association with Chromosomal Aneuploidies (detected in ~50% of cases).
  • Turner Syndrome (45,XO): Most classic USMLE association.
  • Trisomy 21 (Down Syndrome), Trisomy 18 (Edwards), Trisomy 13 (Patau).
• Clinical features
  • Present at birth as a soft, compressible, painless, posterior triangle neck mass
  • Can cause dysphagia or airway compromise
  • Positive transillumination test