Some<unk> s do not cause any symptoms, in which case they may be discovered incidentally on a CT scan performed for a different purpose. Symptoms such as abdominal or back pain or pressure, diarrhea, indigestion, or yellowing of the skin and whites of the eyes can arise from the effects of a larger<unk><unk> , either locally or at a metastasis. About 40% of<unk> S have symptoms related to excessive secretion of hormones or active polypeptides and are accordingly labeled as "functional"; the symptoms reflect the type of hormone secreted, as discussed below. Up to 60% of<unk> s are nonsecretory or nonfunctional, in which there is no secretion, or the quantity or type of products, such as<unk>  polypeptide (PPoma), chromogranin A, and neurotensin, do not cause a clinical syndrome although blood levels may be elevated. In total, 85% of<unk> s have an elevated blood marker. Functional<unk> s are often classified by the hormone most strongly secreted, for example: * gastrinoma: the excessive gastrin causes Zollinger–Ellison syndrome (ZES) with peptic ulcers and diarrhea * insulinoma: hypoglycemia occurs with concurrent elevations of insulin, proinsulin and C peptide * glucagonoma: the symptoms are not all due to glucagon elevations, and include a rash, sore mouth, altered bowel habits, venous thrombosis, and high blood glucose levels * VIPoma, producing excessive vasoactive intestinal peptide, which may cause profound chronic watery diarrhea and resultant dehydration, hypokalemia, and achlorhydria (WDHA or<unk>  cholera syndrome) * somatostatinoma: these rare<unk> s are associated with elevated blood glucose levels, achlorhydria, cholelithiasis, and diarrhea * less common types include ACTHoma, CRHoma, calcitoninoma, GHRHoma, GRFoma, and parathyroid hormone–related peptide<unk>  In these various types of functional<unk> s, the frequency of malignancy and the survival prognosis have been estimated dissimilarly, but a pertinent accessible summary is available.
Pancreatic neuroendocrine tumor
Small intestine neuroendocrine tumor
Metastatic insulinoma
Acinar cell carcinoma of the pancreas
Glucagonoma
Pancreatic mucinous cystic neoplasm
Insulinoma
Goblet cell carcinoid