This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Surgery
[{'content': 'A 58-year-old woman undergoes excision biopsy of a tumor in the left posterior triangle of her neck. Histology suggests that this is a metastatic cancer. What is the most likely site of the primary tumor? \nSelect and explain. \nA. Ovary, B. Adrenal gland, C. Kidney, D. Piriform fossa', 'role': 'user'}, {'content': 'Answer: D \nExplanation: More than 80% of neck gland tumors arise from structures above the clavicle. The piriform fossa is lateral to the aryepiglottic folds and is a major site where a primary cancer may remain hidden from early detection. Twenty percent of neck gland tumors are primary and 80% represent metastatic disease.', 'role': 'assistant'}]