Mixed ependymoma-neuroendocrine tumor of the lateral ventricle.

A histologically unique glioneuronal neoplasm occupying the lateral ventricle of a child was immunohistochemically and ultrastructurally characterized. Its principal component exhibited the characteristic features of ependymoma, whereas a minor population of neuroendocrine cells, occurring singly and in small clusters, lay scattered throughout the ependymoma component. Yet another unusual finding was the presence of numerous elastic fibers within the extracellular matrix. This tumor is considered to represent a true mixed neoplasm consisting of ependymal and neuroendocrine elements.