Immunohistochemical Expression of Synaptophysin in Brain Tumors

ABSTRACT

BACKGROUND: Perikaryal or perikaryal surface immunostaining for synaptophysin has been posited to distinguish the neoplastic neuronal elements of gangliogliomas from entrapped non-neoplastic neurons in other gliomas of various types. However, recent studies revealed that perikaryal surface immunoreactivity can be seen in the neurons of normal human spinal cords and brains, as well as in the brain tissues around certain non-neuronal lesions. To access the validity of this criterion in the diagnosis of ganglion cell neoplasms, we evaluated patterns of immunostaining of synaptophysin in neuronal, glial and some non-neuroepithelial tumors. METHODS: We selected 104 cases of gangliogliomas, gangliocytomas, central neurocytomas, dysembryoplastic neuroepithelial tumors, astrocytomas, oligodendrogliomas, glioblastomas, a pleomorphic xanthoastrocytoma, meningiomas, arterio-venous malformations, craniopharyngiomas, a foreign body granuloma, temporal lobe epilepsies, and autopsied brains. A representative block including the gray matter was identified for each case, and synaptophysin immunostaining was performed. RESULTS: Perikaryal and perikaryal surface immunoreactivity for synaptophysin was observed in the neurons of various types of lesions. Percentage of perikaryal and perikaryal surface immunoreactivity of the gangliogliomas, glial tumors, and non-neuroepithelial lesions were 100%/93%, 80%/58% and 57%/26%, respectively. CONCLUSIONS: Although synaptophysin positive neurons are found in the ganglioglioma, these patterns are clearly not pathognomonic for glioneuronal tumors.