Synaptophysin is a membrane glycoprotein found in presynaptic vesicles and is commonly used as an immunohistochemical marker for cells of neuronal (e.g. gangliogliomas) and neuroendocrine lineage (e.g. pheochromocytomas and paragangliomas).

In the brain, it has been suggested that perisomatic synaptophysin immunohistochemical staining is not seen in normal neurons and therefore is a reliable feature to distinguish neoplastic from non-neoplastic neurons. It appears, however, that this is not always the case; normal brain, as well as non-neoplastic brain tissue, can show synaptophysin staining .