Anterior Midline Swelling of the Neck

Classification: From Above Downwards

Key Differentials in Detail

1. Thyroglossal Duct Cyst (Most Important)

• 65% below the hyoid bone
• 15% at the level of the hyoid bone
• 75% are in the midline; up to 2 cm off-midline is possible

• Painless midline neck mass, mostly in children
• Moves upward on swallowing AND on tongue protrusion - this is the hallmark sign
• May become infected (pain, redness, swelling) and rupture, forming a discharging sinus
• Rarely causes dysphagia or dyspnoea
• 1% risk of malignancy (classically papillary thyroid carcinoma)

• Ultrasound: homogeneous anechoic cystic mass with posterior wall enhancement (see image below), or pseudosolid if infected/hemorrhagic
• CT/MRI: invariably high T2 signal; variable T1 depending on protein content
• Must confirm presence of normal thyroid tissue in the normal location (rare cases represent the only functioning thyroid tissue)

Ultrasound: midline infrahyoid homogeneous anechoic cystic mass with posterior wall enhancement (thyroglossal duct cyst) - Scott-Brown's Otorhinolaryngology

• Excision of the cyst + central body of the hyoid bone + the entire suprathyoid tract through to the tongue base (foramen caecum)
• Removal of the hyoid body is essential because the duct is intimately related to it; failure to do so causes recurrence
• Complete excision minimizes recurrence from small side branches of the tract

2. Goitre (Thyroid Swelling)

• Moves up on swallowing but does NOT move on tongue protrusion
• Can involve the isthmus or pyramidal lobe presenting as a midline mass
• May extend retrosternally (retrosternal goitre)
• Confirmed on ultrasound; thyroid function tests and FNAC required

3. Dermoid Cyst

• Can occur anywhere in the midline
• Sublingual dermoid: in the submental region above the hyoid
• Does NOT move with swallowing or tongue protrusion
• Doughy consistency, may contain hair/teeth/sebum
• Does not transilluminate (cf. cystic hygroma)

4. Subhyoid Bursitis

• Located at the level of the hyoid bone
• Moves on swallowing
• Can mimic a thyroglossal cyst clinically

5. Ludwig's Angina

• Acute, life-threatening bilateral cellulitis of the floor of mouth and submental space
• Tender, boardlike swelling in the submental region
• Associated with dental infection (usually lower 2nd/3rd molars)
• Elevation of tongue, drooling, risk of airway compromise

6. Submental Lymph Nodes

• Enlarged lymph nodes in the submental triangle
• Reactive (dental/lip/tongue infection) or malignant (floor of mouth Ca)
• Multiple, discrete or matted
• Do not move with swallowing or tongue protrusion

7. Cystic Hygroma (Lymphatic Malformation)

• Congenital lymphatic malformation; presents at birth or in infancy
• Soft, compressible, brilliantly transilluminant (pathognomonic)
• Increases in size on crying/coughing
• Often bilateral, may extend to face/tongue/floor of mouth
• Management: complete excision or sclerotherapy (OK-432, bleomycin)

Diagnostic Approach Summary

Sources

• Sabiston Textbook of Surgery, Chapter on Thyroglossal Duct Cyst
• Bailey and Love's Short Practice of Surgery, 28th Ed., Thyroglossal Duct Cysts
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery, TDC and neck swelling imaging
• S. Das - Manual on Clinical Surgery, 13th Ed., Differential Diagnosis of Neck Swellings