The fine structure of the isomorphic oligodendroglioma.

The fine structure of 26 isomorphic oligodendrogliomas excised from various areas of the Central Nervous System is described. These tumors are composed mainly of three types of cells: (a) those with large round or ovoid nuclei and scanty cytoplasm, (b) those with abundant cytoplasm, very rich in organelles and (c) cells very fibrillated with long cellular processes. The cytoplasm of the second cell type sometimes included crystalline bodies, numerous microtubules, myelin-like membranous structures and a large number of elongated mitochondria. The cells with the very fibrillated cytoplasm are eigher astrocytes intermixed with the neoplastic cells of the oligodendrocytic line or an astrocytic-like cellular evolution of the immature neoplastic cell of the oligodendrocytic line. Ultrastructural analysis provided evidence that isomorphic oligodendroglioma is not as homogeneous as was considered to be at the light microscopy level.