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: Surgery
Percentage of pheochromocytoma that are bilateral is: 
Select and explain. 
A. <1%, B. 1-5%, C. 10%, D. 25%
C: 10%
Answer: C: 10% 
Explanation: Pheochromocytomas often are called the 10 percent tumor because 10% are bilateral, 10% are malignant, 10% occur in pediatric patients, 10% are extra-adrenal, and 10% are familial. Ref: Schwaz's principle of surgery 9th edition, chapter 38.