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: Medicine
Which is the least malignant pancreatic endocrine tumor ? 
Select and explain. 
A. Zollinger-Ellison syndrome, B. Insulinoma, C. VIPoma, D. Glucagonoma
B: Insulinoma
Answer: B: Insulinoma 
Explanation: Insulinoma patients generally presents with hypoglycemia symptoms. Mainly located in the pancreas, and malignancy is <10%. Reference: Table 350-2, Harrisons Principles of Internal Medicine, 18th Edition, Page 3057