The root cause of Zollinger-Ellison Syndrome is not known but how this syndrome develops is quite significant. This disease begins with the development of tumors in the pancreas or duodenum. There may also be tumors in the lymph nodes adjoining the pancreas. The pancreas is situated behind the stomach and is responsible for producing enzymes that help in digestion. The pancreas also produces hormones which help in controlling acid formation in the stomach. The juices secreted by the pancreas, duodenum, and the liver get mixed in the duodenum. This is where maximum digestion of food takes place. The tumors formed in Zollinger-Ellison Syndrome are constituted of cells that produce excessive gastrin as a result of which there is excessive gastric production in the stomach. The excessive production of acid then results in formation of peptic ulcers. These tumors may at times become malignant. The growth of the tumor may be slow but the spread of the cancer in the adjoining areas like the lymph nodes or the liver may be rapid.