This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Urology, Subject name: Surgery
Commonest endocrine tumor of pancreas 
Select and explain. 
A. A cells, B. B cells, C. Delta cells, D. VIPoma
B: B cells
Answer: B: B cells 
Explanation: Insulinomas- arising from B cells of pancreas- are the commonest endocrine pancreatic tumour(60%). Gastrinomas - arising from non-beta cells (G cells) of the pancreas- are the 2nd most common endocrine pancreatic tumour. Then comes Glucagonomas (arising from A cells) and VIPomas (arising from D2 cells of pancreas). Reference : page 709-10 SRB's manual of surgery 5th edition