Glioma

GLIOMA, glioma, glioblastoma, a tumor consisting of elements of the intermediate tissue of the nervous system, neuroglia (see); the participation of mesenchymal elements in glioma varies greatly; sometimes glioma contains many vessels, interlacing in it or of the cavernous angioma type or in the form of telangiectases (g. teleangiectodes); in these cases gliomas are particularly prone to hemorrhage, e.g. with minor traumas (apoplectic gliomas); sometimes hemorrhages destroy the tumor so much that the diagnosis of the case is possible only with careful microscopic examination. In some gliomas extensive necroses, lime deposits, fatty degeneration, formation of cavities (g. cysticum) are found; cysts can also arise from the expansion of epithelial inclusions observed in these tumors and representing parts or undifferentiated epithelium of the central canal (ependyma) or embryonic epithelium of the neural tube; in the first case the epithelium is single-layered glandular (hence the term adenoglioma), in the second multi-layered. Gliomas with epithelial formations are also called gliomatous neuroepitheliomas, spongioblastomas, or spongioneuroblastomas (Schiffert), which is intended to emphasize the various degrees of maturity of the original elements of the neural tube. Gliomas are usually solitary, occur mainly in the gray and white matter of the brain or spinal cord, often near the central canal and in the wall of the ventricles; they are the most frequent brain tumors; gliomas are rarely found in peripheral nerves, e.g. in the acoustic nerve; gliomas of the retina are more frequent. Individual cases of glioma of the nose (probably in connection with hydrocephalocele), tongue, posterior lobe of the pituitary gland, and lung have been described. The size of glioma varies from a millet seed to a large apple; the shape is usually round, sometimes spindle-shaped. The tumor grows slowly, for years, generally (with extremely rare exceptions) does not metastasize. On section, glioma has the appearance of a grayish-white or pinkish nodule; sometimes it is dark red; the contours of the tumor are usually indistinct; often microscopically it is difficult to separate the tumor tissue from healthy parts, especially since reactive proliferations of glia are often observed around the periphery of gliomas, interpreted by some authors as infiltrative growth of the tumor. Very rarely do gliomas grow beyond the substance of the brain, for example they penetrate the meninges, bones (see Gliosarcoma). On microscopic examination it is found that they consist of neuroglial cells with their processes [see separate table (vol. VI, art. 268-269), fig. 3]; the interlacing of these plasmatic processes with a certain admixture of fibrous glia constitutes the basis of the tumor. More dense gliomas (g. durum) are richer in fibrous glia, contain few cells, they are poor in protoplasm, and their nuclei are the smallest [see separate table (vol. VI, art. 268-269), fig. 4]; soft gliomas (g. molle) are very rich in cells, nuclei are large, often irregular, the content of fibers is insignificant; due to the great similarity with sarcomas they are also called glioplastic sarcomas, or gliosarcomas (see). Sometimes giant gliotic cells (Monstrezellen, Kolossalzellen of German authors) are found in glioma - so-called giant-cell gliomas, sometimes containing a peculiar granularity and pigment (pigmented glioma). Some gliomas, on the other hand, turn out to be built from those neuroglial cells which are usually distinguished under the name astrocytes (see); such gliomas are called: astrocytoma (see). Gliomas with gelatinous edema of the tissue are called myxogliomas. Often cells and fibers in glioma are arranged like a picket fence or rows of chains connecting the processes of the soft meninges, its vessels [see separate table (vol. VI, art. 268-269), fig. 5]; in this case peculiar radiating, radial structures, rosettes arise; these phenomena are common for gliomas with the above epithelial formations. Ganglion cells and nerve fibers in the vicinity of glioma often exhibit signs of degeneration, and on the other hand, sometimes their preservation is observed even inside the tumor itself; this probably explains the frequent discrepancy between clinical symptoms of deficit and the volume or location of the tumor. A feature of spinal cord gliomas is, on the one hand, their tendency to spread along the length of the organ, giving a diffuse thickening of it, and on the other hand, a clearly expressed tendency to decay, formation of cavities - so-called gliomatous syringomyelia, or central gliomatosis. There are indications of a connection of such forms with irregularities in the development of the neural tube; however, the same can be said about glioma in general; for instance, the occurrence of these tumors in newborns and in early childhood can speak for their congenital nature, their coincidence with a number of obvious deformities both on the part of the central nervous system (e.g. spina bifida, tuberous sclerosis) and other organs (heart, kidneys). Cases of the occurrence of glioma after trauma have been described; it is assumed that here they develop from gliotic scars. Treatment is surgical, not always technically possible, however (for example, spinal cord glioma).