Branchial cyst

What it is

A branchial cleft cyst is a remnant of the second branchial cleft, the most common of the branchial clefts, and it follows failure of obliteration of that cleft. Three malformations are described: a branchial fistula, a persistent communication between skin and GI tract; a branchial sinus, a blind-ended tract opening to skin; and a branchial cyst, a persistent cervical sinus with no external opening. Among neck masses it belongs to the anterior triangle group, and in the differential of neck masses it sits with the congenital masses alongside dermoid cyst, thyroglossal duct cyst, laryngocele and ectopic thyroid tissue.

How it presents

The cyst is a smooth, painless, slowly enlarging lateral neck mass of the anterior triangle, often following a URTI. The swelling lies in the upper part of the neck anterior to the sternocleidomastoid muscle, in the upper third of the anterior neck triangle, and it can be felt between that muscle and the pharynx. It is smooth, round, non-tender, fluctuant and non-transilluminant, and it does not move during swallowing and does not move on tongue protrusion. The swelling can be intermittent, soft and fluctuant. Erythema and tenderness appear if it is infected, and there is a painful increase in size at the time of a URTI. Typically it is a benign, lateral, unilateral neck mass.