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': 'Rarest type of thyroid carcinoma is \nSelect and explain. \nA. Papillary, B. Follicular, C. Medullary, D. Anaplastic', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Undifferentiated (anaplastic) carcinoma\nThis is one of the most aggressive malignancies in humans.\xa0\nThankfully it is rare. It may develop de novo, or present as dedifferentiation of a papillary or poorly differentiated carcinoma. The disease is characterised by rapid growth, visceral invasion\xa0 and\xa0 distant\xa0 metastases.\xa0The\xa0 surgeon’s\xa0 role\xa0 in\xa0 this disease is crucial. Thyroid lymphoma can be incorrectly diagnosed as anaplastic cancer and so biopsy is critical. This can be done using a core or open technique.\nReference: Bailey & Love’s short practice of surgery , 27th\xa0 ed page no 816', 'role': 'assistant'}]