This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Gland, Subject name: Surgery
[{'content': 'Long standing multinodular goiter leads to: \nSelect and explain. \nA. Follicular Ca thyroid, B. Colloid carcinoma, C. Medullary Ca, D. Papillary Ca', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Follicular Ca thyroidRef: Bailey and Love 26th edition, Page 765* Longstanding MNG can lead to follicular cancer.* Previous irradiation leads to papillary cancer.', 'role': 'assistant'}]