A 35-year-old woman presents with a painless, slowly enlarging neck swelling at the anterior border of the sternocleidomastoid at the junction of the upper and middle thirds. It has been present since childhood. Aspiration yields milky-white fluid. The most likely diagnosis is:
- A Thyroglossal duct cyst
- B Dermoid cyst
- C Branchial cyst (second arch cyst) ✓
- D Cystic hygroma (macrocystic lymphatic malformation)
Correct answer: C. Branchial cyst (second arch cyst)
Explanation
A painless neck swelling at the anterior border of the SCM (junction of upper and middle thirds), containing milky-white fluid, presenting in early adulthood is characteristic of a second branchial cleft cyst. Aspiration yields cholesterol-rich milky fluid with cholesterol crystals (the classic Boykin fluid). Thyroglossal cysts are midline and move with tongue protrusion. Cystic hygroma typically presents at birth with transilluminability.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.