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': 'For which one of the following tumors, Gastrin is a biochemical marker - \nSelect and explain. \nA. Medullary carcinoma of thyroid, B. Pancreatic neuroendocrine tumor, C. Pheochromocytoma, D. Gastrointestinal stromal tumor', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Gastrin is secreted by Gastrinomas.\nGastrinomas are neuroendocrine tumors found in\n\n\nDuodenum (50 to 70%)\nPancreas (20 to 40%) and\xa0\nOther intraabdominal sites (mesentry, lymph nodes, biliary tract, liver; stomach, ovary).', 'role': 'assistant'}]