PLAB-0292

A 2 year old boy was brought to the physician by his mother with a history of a swelling on the right side of his neck that is extending from the angle of mouth to the middle 1/3rd of sternocleidomastoid muscle. On examination the swelling was on the anterolateral aspect of the muscle and was found to be brilliantly transilluminant. Which of the following is the most likely diagnosis?