A tumor derived from branchial epithelium or branchial rests. (Dorland, 27th ed)

(branchial cyst) A branchial cyst is a remnant of embryonic development resulting from a failure of obliteration of a branchial cleft and consists of a subcutaneous cystic mass. Cysts are located anterior or posterior to the ear or in the submandibular region.

(branchial cleft cyst) A congenital epithelial cyst that develops due to failure of obliteration of the second branchial cleft during embryonic development. It appears as a lump on the side of the neck.

(second branchial cleft anomaly) A rare otorhinolaryngological malformation characterized by the presence of a cyst, sinus or fistula occuring along the anterior border of the sternocleidomastoid muscle. Second branchial cleft fistulae ans sinuses present with skin opening with chronic discharge and recurrent infections, whereas second branchial cleft cysts present as a painless, nontender, stable in size or slowly enlarging lateral neck masses. Cysts occasionally acutely increase in size during upper respiratory tract infection, leading to respiratory compromise, torticollis, and dysphagia.

Branchial cleft cysts are congenital epithelial cysts, which arise on the lateral part of the neck from a failure of obliteration of the second branchial cleft in embryonic development. Phylogenetically, the branchial apparatus is related to gill slits.