The
central neurocytoma, a recently identified rare supratentorial
brain tumor in young adults, is characterized by intraventricular location and a usually benign
clinical course. In order to elucidate the histogenesis and differentiation potential of this
neoplasm, we have undertaken an immunocytochemical and molecular
biological study of four
central neurocytomas. It was found by immunocytochemistry and immunoblotting that all
tumors express
neuron-specific enolase and
synaptophysin. Western blots also revealed expression of the synaptic vesicle
protein,
synapsin I,
neurofilament protein and
glial fibrillary acidic protein in several
neurocytomas which failed to exhibit immunoreactivity to these
marker antigens on
paraffin sections. Immunocytochemical reactions with
antibodies to
synaptophysin and
glial fibrillary acidic protein on adjacent sections demonstrated coexpression in individual
tumor cells. The neuronal form of the pp60src
protein-tyrosine kinase, an
oncogene-product specifically expressed in central nervous system neurons, was not detectable in two
central neurocytomas investigated. N-myc, a proto-oncogene frequently amplified in childhood
neuroblastomas, was present as a single copy gene in all
central neurocytomas, indicating that amplification of this gene is not involved in the pathogenesis of the
central neurocytoma. In accordance with ultrastructural evidence of synaptogenesis, we conclude that the
central neurocytoma is a
neuroectodermal tumor with consistent commitment for neuronal differentiation. Since these
tumors retain a potential for additional glial differentiation, we propose an origin from bipotential progenitor cells in the periventricular matrix, which in the mammalian brain persists throughout adult life.