<prompt> MC site of gastrinoma:-DuodenumPancreasStomachColon  <response>: Agastrinomais a gastrin-producing tumor usually located in the pancreas or the duodenal wall. Gastric acid hypersecretion and aggressive, refractory peptic ulceration result Zollinger-Ellison syndrome.Diagnosisis by measuring serum gastrin levels. Treatment is proton pump inhibitors and surgical removal. 