Tumors of ependymal origin are considered rare. In an analytic study of 140 gliomas from the neurosurgical service here, eight were found to be tumors composed of cells of ependymal derivation. Five of these had their origin in the cerebrum, while three grew within the fourth ventricle. Although this is a small collection on which to base definite conclusions, certain clinical and histologic observations seem to warrant a report of these cases.
HISTOLOGIC METHODS
In the histologic study of these ependymal gliomas, the following staining methods were used: (1) hematoxylin and eosin; (2) Mallory's phosphotungstic acid-hematoxylin; (3) Bailey's neutral ethyl violetorange G; (4) Hortega's silver carbonate for oligodendroglia; (5) Penfield's second modification of Hortega's silver carbonate for oligodendroglia; this method proved valuable in staining tissue that had been preserved in formaldehyde for a long time; (6) a modification of Hortega's silver carbonate (lithium) method for impregnating astrocytes, with sections cut