Causes of Branchial Cleft Cyst
Branchial cleft cysts form during the stages of embryonic development. They happen to occur when the tissues in the neck and collarbone area, also known as branchial cleft, fail to develop as they do in normal cases. As has already been mentioned, they appear as open spaces on either or both sides of the neck. These open spaces are called cleft sinuses. These cysts may form from the fluid drained from a sinus.

Types
There are basically two types of these cysts, primary and secondary. They are grouped in accordance with their embryologic derivation. The primary type are found in the preauricular area. They are not painful to touch. The secondary type are present anywhere along the anterior margin of the sternocleidomastoid muscle. They are tender, particularly when infected. The infected branchial cleft cysts must be treated with antibiotics immediately.