This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroid Tumor, Subject name: Pathology
[{'content': 'All of the following are features of medullary carcinoma of thyroid, except: \nSelect and explain. \nA. Arises from parafollicular cells or C-cells, B. Known association with MEN-2A or MEN-2B syndromes, C. RAS gene mutations plays an impoant role in its tumourigenesis, D. Tumour cells secrete calcitonin', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Activating point mutations in RET proto-oncogene is associated with both familial & sporadic medullary carcinomas. RAS gene mutation is associated with follicular cancer of thyroid. Hence, option-3 is wrong Medullary thyroid carcinoma Neuroendocrine neoplasms derived from parafollicular cells, or C cells. Medullary carcinoma cells similar to normal C cells, secrete calcitonin. Hence, measurement of calcitonin levels plays impoant role in diagnosis & postoperative follow-up of patients. Cases associated with MEN types 2A or 2B, tumor can occur in younger patients & may even arise during first decade of life. MEN-2A Medullary thyroid carcinoma Pheochromocytoma Parathyroid adenoma MEN-2B Medullary thyroid carcinoma Pheochromocytoma Marfanoid habitus Mucosal neuromas', 'role': 'assistant'}]