<prompt> True about branchial cysta Seen deep to lower 13 of sternocleidomastoidb Wall consists of lymphoid tissuec Filled with straw coloured fluid with cholesterol crystalsd Presents at birthacbcad  <response>: A branchial cyst probably develops from the vestigial remnants of the second branchial cleft, is usually lined by squamous epithelium and contains thick, turbid fluid, full of cholesterol crystals... Microscopic examination of these cysts commonly shows a layer of lymphoid tissue and the modern theory is that these cysts may arise as a result of branchial epithelium entrapped within a lymph node. - Bailey 