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': 'A patient with long-standing multinodular goitre develops hoarseness of voice; also, the swelling undergoes a sudden increase in size. Likely diagnosis is \nSelect and explain. \nA. Follicular ca, B. Papillary ca, C. Medullary ca, D. Anaplastic ca', 'role': 'user'}, {'content': 'Answer: A \nExplanation: History of sudden growth in a long-standing goitre and hoarseness are suggestive of malignant change.\nMost common carcinoma to develop in developing in long-standing multinodular goitre is Follicular carcinoma.', 'role': 'assistant'}]