Abstract
The two most commonly used immunohistochemical markers for neuroendocrine tumors are chromogranin A and synaptophysin. We had previously studied immunohistochemical staining on pancreatic neuroendocrine tumors: chromogranin A strongly positive tumors including gastrinomas, glucagonomas, pancreatic polypeptidomas were more malignant (>50%) than chromogranin A weakly positive tumors of insulinomas (<10%). With additional 40 cases of gastroenteric neuroendocrine tumors, formerly carcinoid tumors, we investigated chromogranin A and synaptophysin immunostaining: more aggressive neuroendocrine tumors of duodenum, small intestine and ascending colon were strongly positive for chromogranin compared to less aggressive neuroendocrine tumors of sigmoid colon and rectum. Immunohistochemical staining for chromogranin A represents a marker for the secretary granules with a possible marker of prognosis on all gastroenteropancreatic neuroendocrine tumors. Furthermore, serum CgA levels may be used as an indirect, independent diagnostic and prognostic marker for gastroenteropa-ncreatic neuroendocrine tumors in three folds: First to diagnose gastroenteropancreatic neuroendocrine tumors. Secondly, to assess the degree of malignancy by tissue and serum CgA levels and thirdly, evaluate increasing serum CgA levels as a prognostic indicator. Since there is no difference of immunostaining for synaptophysin between more aggressive neuroendocrine tumors and less aggressive tumors, immunostaining for synaptophysin is not a marker for aggressive tumors.