An immunohistochemical study of the primitive and maturing elements of human cerebral medulloepitheliomas.

Four examples of human cerebral medulloepithelioma were studied immunohistochemically with a panel of antibodies and antisera to neuronal and glial proteins. The tumors, in addition to primitive medullary epithelium, contained areas of neuroblastic, ganglionic, astrocytic, ependymoblastic and ependymal differentiation, and in one tumor, areas resembling polar spongioblastoma. Tumor cells throughout the primitive medullary epithelium displayed focal immunoreactivity for vimentin, glial fibrillary acidic (GFA) protein and for the neuron-associated class III beta-tubulin isotype. Neuroblasts showed immunoreactivity for the class III beta-tubulin isotype, microtubule-associated protein 2 and neuron-specific enolase. Immunoreactivity for neurofilament epitopes and synaptophysin was detected in areas of ganglionic differentiation and coincided with the demonstration of neurofibrils in Bielschowsky's silver impregnations. Vimentin was the only marker detected in ependymoblastic and ependymal rosettes or in areas of polar spongioblastoma, as well as in mesenchymal cells. The results indicate that, even in very primitive neoplastic neuroepithelium, immunocytochemical evidence of early commitment of some of the cells to a neuronal or glial lineage can be demonstrated. The neuron-associated class III beta-tubulin isotype appears to be one of the earliest markers indicative of neuronal differentiation in normal and neoplastic primitive neuroepithelium.