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: Pathology
[{'content': 'The expression of the following oncogene is associated with a high incidence of Medullary carcinoma of thyroid - \nSelect and explain. \nA. P53, B. Her2/neu, C. RET proto-oncogene, D. Rb gene', 'role': 'user'}, {'content': 'Answer: C \nExplanation: RET protooncogene is a growth factor receptor (receptor tyrosine kinase) \nThe RET protein is a receptor for the glial cell lined derived neurotrophic factor and structurally related proteins that promote cell survival during neural development.\nRET is normally expressed in the following cells\n\n\nParafollicular C cells of the thyroid\nAdrenal medulla\n\n\nParathyroid cell precursors. Point mutation in the RET protooncogenes are associated with the following disorders.\n\n\xa0(i) MEN type 2A -\n\n\nThere is point mutation in RET extracellular domain which causes constitutive dimerization and activation leading to:-\nMedullary thyroid carcinoma\nAdrenal and parathyroid tumours\n\n(ii) MEN type 2B -\nPoint mutation in the RET cytoplasmic catalytic domain alter the substrate specificity of the tyrosine kinase and leads to:-\nThyroid tumours\nAdrenal tumors\n(iii) Sporadic Medullary thyroid carcinoma \n\nSomatic rearrangement of the RET gene\n\n(iv) Hirschsprung disease\n\nThis is caused by complete loss of RET function.', 'role': 'assistant'}]