Synaptophysin

Synaptophysin is a glycoprotein (38KD), localized to presynaptic neurosecretory vesicles, such as synaptic vesicle membrane, cytoplasmic vesicles, secretory vesicles, and synaptosome, in the brain and endocrine cells, including islets cells in the pancreas. Pancreatic islets cells are usually used for positive control and as cytoplasmic staining for immunohistochemistry testing.

Synaptophysin expression is often seen in well-differentiated neuroendocrine tumor (carcinoid tumor), neuroendocrine carcinoma, neuroblastoma, adrenal cortical tumors, paraganglioma, pheochromocytoma, Merkel cell carcinoma, parathyroid tumor, and medullary thyroid carcinoma. Synaptophysin has been frequently used in conjunction with chromogranin A, INSM1 and CD56 for the identification of neuroendocrine tumors.