Branchial Cyst — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Branchial CystMFDS Part 1

A 19-year-old woman presents with a three-year history of a slowly enlarging, painless neck swelling. Examination reveals an isolated, smooth, fluctuant mass at the junction of the upper and middle thirds of the anterior border of the sternocleidomastoid muscle. It does not move on swallowing or protrusion of the tongue. What is the most likely diagnosis?

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Correct answer: D — Branchial cyst

A branchial cyst is the best diagnosis. It classically presents in a young person as a smooth, fluctuant lateral neck swelling near the junction of the upper and middle thirds of the anterior border of sternocleidomastoid; most are associated with the second branchial apparatus. A thyroglossal duct cyst is usually midline and characteristically moves with tongue protrusion. Cystic hygroma generally presents earlier in life and commonly involves the posterior triangle. A carotid body tumour is a solid, often pulsatile mass near the carotid bifurcation. Cervical metastasis is less likely given the patient's age, long history and fluctuant lesion, but a new cystic lateral neck mass in an adult over 40 must be treated as possible nodal metastasis until proved otherwise.

Reference: McKiernan DC. Neck Swellings: Branchial Cleft Cyst section. BMJ. 2014;348:g1078. https://www.bmj.com/content/391/bmj-2025-086142.full.pdf