NCIt definition : A gastrin-producing neuroendocrine tumor. It is usually located in the pancreas but
it is also found at other anatomic sites, including the stomach and small intestine.;
Alternative definition : NCI-GLOSS: A tumor that causes overproduction of gastric acid. It usually begins in
the duodenum (first part of the small intestine that connects to the stomach) or the
islet cells of the pancreas. Rarely, it may also begin in other organs, including
the stomach, liver, jejunum (the middle part of the small intestine), biliary tract
(organs and ducts that make and store bile), mesentery, or heart. It is a type of
neuroendocrine tumor, and it may metastasize (spread) to the liver and the lymph nodes.;