A 25-year-old male presents with a painless neck swelling at the anterior border of the sternocleidomastoid muscle at the junction of the upper and middle thirds. The swelling transilluminates and has no pulsations. It has been present since childhood. The most likely embryological remnant is:
- A Thyroglossal duct cyst arising from persistent thyroglossal duct
- B Second branchial arch cyst arising from the cervical sinus of His ✓
- C First branchial cleft cyst in relation to parotid
- D Cystic hygroma from lymphatic sac
Correct answer: B. Second branchial arch cyst arising from the cervical sinus of His
Explanation
A cystic neck swelling at the anterior border of the SCM at the junction of upper and middle thirds is the classic location of a second branchial cleft cyst. It arises from incomplete obliteration of the cervical sinus of His (formed by the overgrowth of the second arch over the third and fourth arches). It presents in young adults when it enlarges or becomes infected. The classic fistula would open at this same location on the skin and track through the carotid bifurcation to the tonsillar fossa. Thyroglossal cysts are midline and move on tongue protrusion.
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.