[Fine structure of glioblastoma multiforme with "adenoid formation"].

Glioblastoma multiforme with "adenoid formation" (Kepes) in the temporal lobe of a 70 year old man was presented. In addition to the classical features of glioblastoma multiforme, the tumor presented a pattern of anastomosing trabeculae of polygonal cells, mimicking epithelial tubules, in a myxoid stroma. On electron microscopic examination, the tumor cells were devoid of well-developed cytoplasmic processes. The cytoplasm of some tumor cells contained glycogen particles and lipid vacuoles in addition to usual organelles. The cell surface was partly covered by basal lamina associated with half desmosomes and had occasional filopodia-like cytoplasmic projections. A few tumor cells contained a dense intracytoplasmic accumulation of glial filaments. Intercellular junctional complexes were poorly developed. There was no evidence of differentiation of tumor cells toward ependymal cells or epithelial cells. These electron microscopic findings suggest that this tumor is predominantly composed of immature astrocytes. In spite of a superficial resemblance to adenocarcinoma on light microscopy, the tumor cells are devoid of the differentiating features of epithelial neoplasms, and their ultrastructure is essentially similar to that of glioblastoma multiforme.