A 35-year-old presents with a painless lateral neck swelling that moves on swallowing and ascends on tongue protrusion. It is located at the level of the hyoid bone, lateral to the midline, along the anterior border of the sternocleidomastoid. The MOST likely diagnosis is:

• A Thyroglossal duct cyst
• B Cystic hygroma
• C Dermoid cyst
• D Branchial cyst (2nd branchial cleft cyst) ✓

Explanation

A lateral neck cyst along the anterior SCM border between the angle of mandible and the clavicle, typically at the level of the hyoid or just below, is characteristic of a 2nd branchial cleft cyst (most common branchial cyst — 95%). It does NOT consistently move with tongue protrusion (which is specific to thyroglossal cysts). Thyroglossal cysts are midline and move with tongue protrusion. The 2nd branchial cyst is remnant of the cervical sinus and typically found deep to SCM, anterior to it. Cystic hygroma (lymphangioma) is typically in the posterior triangle.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.