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: Pediatrics
[{'content': 'What percentage of pheochromocytomas are malignant? \nSelect and explain. \nA. 5, B. 10, C. 20, D. 15', 'role': 'user'}, {'content': 'Answer: B \nExplanation: b. 10(Ref: Nelson\'s 20/e p 2227-2729, Ghai 8/e p 525)Mnemonic:\'Rule of ten\' for Pheochromocytoma: ("BG MEN"): 10% of Pheochromocytoma are:* Bilateral* Malignant* Extra-adrenal: paragangliomas* Normotensive (No hypertension)Note: 10% of sporadic Pheochromocytoma are bilateral; but 50% of familial tumors are bilateral.', 'role': 'assistant'}]