SYP and colorectal adenocarcinoma: However, it can be difficult in conventional colorectal adenocarcinomas that only reveal their neuroendocrine differentiation when immunohistochemically stained for synaptophysin, the immunohistochemical gold standard for the detection of neuroendocrine differentiation [7,8], which represents an integral membrane glycoprotein that is found in presynaptic vesicles of neurons as well as normal neuroendocrine epithelial cells (e.g., pancreatic islets) [9].