Electron microscopic findings in primitive neuroectodermal tumors of the cerebrum.

The fine structure of 3 primitive neuroectodermal neoplasms of the cerebral hemispheres was studied. The predominant tumor cells were undifferentiated cells with prominent nuclei and scanty cytoplasm containing few organelles. Ultrastructural evidence suggesting differentiation into ependymal, neuronal and possibly astrocytic elements was also present. This study suggests that the cell of origin of this tumor is a primitive multipotential cell of the cerebrum.