Pancreatic neuroendocrine tumors: non-functional
What are non-functioning pancreatic neuroendocrine tumors?
A significant proportion of pancreatic neuroendocrine tumors are not associated with a syndrome related to hormonal hypersecretion. These tumors are referred to as non-functional. They may secrete elevated amounts of hormones such as pancreatic polypeptide, neurotensin, or calcitonin which produce no symptoms in humans. Alternatively, they may produce insignificant amounts of biologically active hormones or inactive forms of hormones. Therefore a non-functioning pancreatic neuroendocrine tumors is defined as a pancreatic tumor of pluripotent endocrine origin with no definable hormonal symptom complex. Most authors estimate that 10-25% of all pancreatic neuroendocrine tumors are non-functional with some series demonstrating an incidence as high as 48%. These estimates make non-functional tumors one of the most common classes of pancreatic neuroendocrine tumors. At operation these tumors are generally larger than their functional counterparts (4.0 vs 1.9 cm) and spread equally throughout the pancreas. Sixty to eighty percent of these tumors are metastatic when diagnosed. This figure compares unfavorably to the 25% incidence of malignancy seen among functioning tumors. When analyzed by molecular, immunohistochemical, or tissue culture techniques, non-functioning tumors usually contain some hormones. No histologic differences between functioning and non-functioning tumors have been described. Serum chromogranin A and pancreatic polypeptide are the most reliable tumor markers.