A GASTRIN-secreting neuroendocrine tumor of the non-beta ISLET CELLS, the gastrin-secreting cells. This type of tumor is primarily located in the pancreas or the duodenum. Majority of gastrinomas are malignant. They metastasize to the liver; lymph nodes; and BONE but rarely elsewhere. The presence of gastrinoma is one of three requirements to be met for identification of zollinger-ellison syndrome, which sometimes occurs in families with multiple endocrine neoplasia type 1; (men 1).