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': 'Screening method of medullary carcinoma thyroid is: \nSelect and explain. \nA. Serum calcitonin, B. Serum calcium, C. Serum alkaline phosphatase, D. Serum acid phosphatase', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Medullary Carcinoma Thyroid (MTC):\n\nNeuroendocrine carcinoma arising from parafollicular ‘C’ cells\xa0of thyroid.\nParafollicular ‘C’ cells are derived from the ultimobranchial bodies\xa0and secrete calcitonin.\n‘C’ Cells are concentrated superolaterally in thyroid lobes, from where MTC usually develops.\nMost MTCs (75-80%) arise sporadically.\nSpread is both lymphatic and hematogenous.\nMC site of metastasis: Liver', 'role': 'assistant'}]