NeuN: a useful neuronal marker for diagnostic histopathology.

The monoclonal antibody A60 specifically recognizes the DNA-binding, neuron-specific protein NeuN, which is present in most neuronal cell types of vertebrates. In this study we demonstrate the potential use of NeuN as a diagnostic neuronal marker using a wide range of formalin-fixed, paraffin-embedded human surgical and autopsy specimens from the central and peripheral nervous system. After microwave antigen retrieval, almost all neuronal populations revealed strong immunoreactivity for NeuN in nuclei, perikarya, and some proximal neuronal processes, whereas more distal axon cylinders and dendritic ramifications were not stained. The stain greatly enhanced the gray matter architecture. NeuN immunoreactivity was not detected in Purkinje cells, most neurons of the internal nuclear layer of the retina, and in sympathetic chain ganglia. We examined nine gangliogliomas and 14 dysembryoplastic neuroepithelial tumors, one ganglioneuroma, and one dysplastic cerebellar gangliocytoma. The neuronal component of all of these lesions showed marked immunoreactivity for NeuN. In addition, NeuN immunoreactivity was focally seen in one of seven medulloblastomas with prominent neuronal differentiation. There was no staining of non-neuronal structures. The results indicate that NeuN immunoreactivity is a sensitive and specific neuronal marker in formalin-fixed, paraffin-embedded tissues, and may be useful in diagnostic histopathology.