This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'The commonest site of Branchial cysts is - \nSelect and explain. \nA. Upper 1/3rd of the SCM, B. Lower 1/3rd of the SCM, C. Upper 2/3rd of the SCM, D. Lower 2/3rd 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.\nBranchial cysts & fistulas \n\nare remnants of the branchial apparatus present in fetal life.\nbranchial cysts, fistulas or sinuses are lined by squamous epithelium.', 'role': 'assistant'}]