Intraventricular neurocytoma with prominent myelin figures.

A case is reported of intraventricular neurocytoma that had characteristic light microscopic findings of neurocytoma with prominent intracytoplasmic concentric lamellar structures mimicking myelin sheaths. On routine H&E-stained sections, this tumor showed intracytoplasmic vesicular bleb-like structures having eosinophilic cores that were consistent with ultrastructural concentric lamellar structures. Immunohistochemically, this tumor was immunoreactive for synaptophysin and neurofilament, but negative for antibody to glial fibriallary acidic protein. Electron microscopic findings fulfilled the criteria for neurocytoma, with the presence of neurosecretory granules and neurotubules. These findings may suggest dual differentiation of this tumor into neurocytes and oligodendrocytes.