A 30 year old man presents with a 5cm neck mass anterior to the sternocleido-mastoid muscle on the left side in its upper third. He states that the swelling has been treated with antibiotics for infection in the past. What’s the most likely cause?

The key is A. Branchial cyst. [ i) Branchial cyst is anterior triangular lump. (parotid is also anterior triangular lump but parotitis regresses with appropriate treatment i.e. becomes normal in size). ii) pharyngeal pouch is posterior triangular lump. iii) Thyroglossal is midline lump. iv) thyroid swelling moves with swallowing].