Tumors may be functional (ie, a clinical syndrome of excessive levels of such hormones as insulin, gastrin, VIP, somatostatin, and glucagon) or nonfunctional (ie, normal serum marker levels [excluding pancreatic polypeptide, chromogranin A]).
Tumors may be sporadic or a manifestation of an inherited endocrinopathy (multiple endocrine neoplasia type 1 [MEN-1], von Hippel-Lindau [VHL]).
Nonfunctional tumors demonstrable via radiologic examination should be resected.