The ultrastructure of oligodendroglioma: personal experience and the review of the literature.

Ultrastructurally, oligodendrogliomas were tumors of rather monotonous appearance, with round and oval nuclei without indentations and cytoplasm of an electron-density lower than that of astrocytic tumors. Cisterns of endoplasmic reticulum and those of Golgi apparatus were occasionally distended. In addition to the usual subcellular organelles, the cytoplasm was rich in ribosomes, microtubules and glycogen granules. Some cellular processes contained branching cisterns, similar to those encountered in human neuroaxonal dystrophies. There are no discernible intermediate filaments. Blood vessels are apparently normal in oligodendrogliomas. Probably, the most characteristic features of oligodendrogliomas are concentric arrays of membranes (so called membrane laminations, whorls or scrolls). A fragment of the cytoplasm sequestrated within a particular whorl may contain mitochondria, lysosomes or abundant glycogen granules. The apparent continuity of membranes of whorls and the channels of endoplastic reticulum is rarely observed.