However, the positivity at immunohistochemical staining for serotonin (57% of patients), CDX-2 (60% of patients) which are markers of neuroendocrine tumors of intestinal origin, and glucagon (80%) and pancreatic polypeptide (100%) which are more typical of pancreatic NETs, was somewhat unexpected and underlines the heterogeneity of the disease and its differences from carcinoids of other districts. Here, GCG is linked to carcinoid tumor.