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Intraventricular tumors may arise from a variety of cells in the region. There are some difficulties in diagnosing these tumors because of their histologically similar appearance. We analyzed intraventricular tumors, including central neurocytoma, oligodendroglioma, cerebral neuroblastoma, and cerebellar neuroblastoma, the neuronal characters of which were established based on their ultrastructural findings, except for oligodendroglioma. Central neurocytoma and cerebellar neuroblastoma showed synaptic formation, and cerebral neuroblastoma possessed immature neurites. Oligodendroglioma showed similar structures to that of a normal oligodendrocyte. Furthermore, we review the literature and evaluate the usefulness of analyzing ultrastructures.

Central neurocytomas are uncommon intracranial neoplasms. More than one hundred cases are documentated in the literature. In this report we describe the clinical and histopathological features in two patients with intraventricular neurocytoma. As the light microscopic features of neurocytoma resemble with that of an oligodendroglioma, it is essential to differentiate these two tumours, using either ultrastructural or immunohistochemical techniques.

Intraventricular neurocytoma, a newly identified disease entity with probably not so rare incidence, has several distinctive clinico-pathological characteristics. Four cases are presented. As in the other cases reported in the literature [1-7], the characteristic features are young age, location close to the junction of the septum pellucidum and foramen of Monro, and well-differentiated neuronal origin pathologically.

A tumor with the clinical and light microscopic appearance of an oligodendroglioma that occurred in the lateral ventricles of a 25-year-old man is described. On further study this tumor proved to have the ultrastructural features typical of neuroendocrine tumors, and the presence of neuron-specific enolase was demonstrated by immunoperoxidase staining. This unusual presentation of a neuroendocrine tumor, which was entirely amitotic and free of atypia, raises important questions concerning both the true incidence of such cerebral differentiated neuroblastomas and their biologic behavior. The importance of electron microscopy and immunostaining techniques, which should be used more frequently to uncover additional cases of this tumor, is stressed.