Ependymoma of the Foramen of Monro: Ultrastructural Characterization

The characteristics of clear cells of an ependy-moma of the foramen of Monro have been studied by electron microscopy to precisely define its or-ganellar composition and to establish the tumor histogenesis. Our data confirm that the once-thought oligodendroglial is, in fact, an ependymal tumor. Both the scarce number of organelles, owing to the low degree of differentiation, and the abun-dance of hyaloplasmic lipid vacuoles can account for the clear appearance of these tumor cells.