This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'Commonest site of branchial cyst is \nSelect and explain. \nA. Upper one third of SCM, B. Lower one third of SCM, C. Upper two third of the SCM, D. Lower two third of the SCM', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Branchial cysts are characteristically found anterior and deep to the upper third of the sternocleidomastoid muscle. Branchial fistulas(those derived from 2nd branchial cleft) open externally in the lower third of necic, near the anterior border of sternocleidomastoid. Its internal orifice is located in the tonsillar fossa. Branchial cysts & fistulas are remnants of the branchial apparatus present in fetal life. branchial cysts, fistulas or sinuses are lined by squamous epithelium. Ref : Bailey & Love 25/e p727', 'role': 'assistant'}]