<prompt> Most frequent site of branchial cyst is atUpper third of posterior border of sternocleidomastoidLower third of anterior border of sternocleidomastoidUpper third of anteromedial border of sternocleidomastoidSupraclavicular fossa  <response>: BRANCHIAL CYSTIt arises from the remnants of second branchial cleft. Normally, 2nd, 3rd, 4th clefts disappear to form a smooth neck. Persistent 2nd cleft is called as cervical sinus of His which eventually gets sequestered to form branchial cyst. Swelling in the neck beneath the anterior border of upper third of the sternomastoid muscle. It is smooth, soft, fluctuant, often transilluminant with a sensation of Half-filled double hot water bottle.It is equal in both sexes. Even though congenital, it is seen in late adolescents and early 3rd decade.It contains cholesterol crystals which is from the lining of mucous membrane which contains sebaceous gland. Cheesy toothpaste like material is typical. 