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 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: Hoarseness of the voice and sudden increase in size of swelling in a patient with multinodular goitre indicate malignant changes. Hoarseness of the voice indicates recurrent laryngeal involvement or vocal cord paralysis. Incidence of Follicular carcinoma is high in endemic goitrous areas, with long standing multinodular goitre, possibly owing to persistent TSH stimulation. Ref: Primary Care Medicine: Office Evaluation and Management of the Adult Patient By Allan H. Goroll, Albe G. Mulley, 2009, Page 736.', 'role': 'assistant'}]