This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pathology
[{'content': 'In which of the following is medullary thyroid cancer is the most aggressive form \nSelect and explain. \nA. MEN type I, B. MEN type II a, C. MEN type II b, D. Sporadic cases', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Medullary carcinoma of thyroid is a characteristic feature of both MEN2A and MEN2B. But it is multifocal and more aggressive in MEN2B compared to MEN2A and sporadic cases. A germline mutation leading to a single amino acid change in RET ,distinct from the mutations in in MEN2A seems to be responsible for almost all cases of MEN2B. (ref:ROBBINS Text book of pathology endocrinology)', 'role': 'assistant'}]