Precervical sinus normally disappears. But if this sinus persists after birth, it forms a cystic swelling at the upper part of the neck, which is called branchial cyst.

Wall of the cyst contains large amount of lymphoid tissue. Because of this the cyst is prone to infection. The contents are viscid, mucoid, cheesy material and cholesterol crystals in large numbers.

Though congenital, yet it does not manifest itself before puberty. Majority of the patients are between 20 to 25 years or even later. Painless swelling in the upper and lateral part of the neck is the main symptom. If infected, the swelling may be painful.

Branchial cyst occupies upper and lateral part of the neck deep to the upper third of the sternomastoid muscle. The branchial cyst develops from the precervical sinus, so it will always be deep to the sternomastoid muscle. It may be round, but it is usually oval in shape with its long axis running forwards and downwards. It is of variable size and may attain the size of an orange. Consistency is soft. When the content is under tension, feel may be firm or even hard.

Fluctuation test is positive. The lump is not freely mobile as it is particularly deep to sternomastoid. On aspiration cholesterol crystals can be demonstrated in the aspirated fluid.

Complications-

1.   Recurrent infection.

2.   Acquired branchial cyst.

Treatment-

Removal of the cyst is the treatment of choice.