Irvin M. Modlin, MD, PhD

Gastroenteropancreatic tumors, although relatively rare, present management problems that may last many years, in comparison with the usually more aggressive adenocarcinomas whose management may encompass a far briefer span of time. In general, 50% of such tumors are insulinomas, while gastrinomas comprise 25%, and nonfunctional tumors 20% VIPomas and glucagonomas are the predominant lesions of the remaining 5%. Clinical diagnosis is usually made on the presence of the classical symptom complex. In uncertain circumstances or covert presentations, the critical diagnostic biochemical test is plasma chromogranin A as well as measurement of the specific peptide.