Branchial cleft cyst or sinus is a rare disorder resulting from incomplete closure of the branchial clefts. The second branchial cleft is implicated much more so than the third cleft. This typically occurs at 4-8 weeks of embryologic growth. Cysts, sinuses, or fistulae can present at birth at the inferior neck. At times these small cysts or skin tag-like remnants contain cartilage. Autosomal dominant inheritance has been reported.

Sometimes a branchial cleft cyst or sinus is not recognized until later in childhood, when it becomes infected. Rarely, it may go unnoticed until it becomes infected in adulthood. A laryngocele may present with a neck mass and is associated with hoarseness and swelling.