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': 'All of the following are helpful for diagnosis of Medullary Ca thyroid except- \nSelect and explain. \nA. Spindle cell stroma with few follicles, B. Amyloid deposition, C. Calcitonin in stroma, D. Histological mitochondria is essential for diagnosis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]