Immunohistochemistry of central nervous system tumors. Its contributions to neurosurgical diagnosis.

Immunofluorescence and immunoperoxidase (peroxidase-antiperoxidase, PAP) techniques for the demonstration of neural and non-neural cell markers are contributing greatly to increase the diagnostic accuracy of difficult tumors of the central nervous system. Well characterized nervous system markers include glial fibrillary acidic (GFA) protein, the three protein subunits of neurofilaments, neuron-specific enolase (NSE), myelin basic protein, and S-100 protein. The most important and reliable of these is GFA protein, which is widely in use for the immunohistochemical diagnosis of tumors of the glioma group. Its many practical applications are reviewed and illustrated. Other neural markers, in particular the specificity of NSE and S-100 protein, need to be critically evaluated. Problems related to the immunohistochemical diagnosis of central neuroepithelial tumors of putative neuroblastic origin remain complex and still need to be resolved. Non-neural markers, such as vimentin, desmin, cytokeratins, Factor VIII, alpha-fetoprotein, human chorionic gonadotropin, and immunoglobulins have well defined, although more restricted, applications in surgical neuropathology.