Historical origin and meaning of the term „glial tumor“

Abstract

In everyday neurosurgical practice, the term „glial tumor“ is associated with astrocytomas, glioblastomas, and oligodendrogliomas, although historically this has not always been the case. The term „glial tumor“ was first given by Virchow in the 19th century as a term initially combining all primary brain tumors under this name. It derives from the name of the group of „supporting“ nerve cells - glia or neuroglia (from the Greek glia - glue), a group which for many years was wrongly ascribed only a cohesive or supporting function.
In 1926, in their classification of glial tumors - A Classification of the Tumors of the Glioma Group on a Histogenetic Basis with a Correlated Study of Prognosis, one of the founding fathers of neuropathology Percival Bailey and the founding father of modern neurosurgery – Harvey Cushing ascribed several different tumors in this group: in addition to neuroepithelioma, spongioblastoma multiforme, astrocytoma and ependymoma, they also add medulloblastoma, astroblastoma, oligodendroglioma and unipolar spongioblastoma. Since then, the classification of glial tumors has undergone many changes to its current form. In the latest classification of brain tumors published in 2021, glial tumors are united in a common group together with glioneuronal and neuronal tumors. Their extensive group includes tumors with different prognosis, age presentation, molecular profile and therapeutic response. From a neurosurgical point of view, the term „glial tumor“ does not carry a prognostic value, but only determines the belonging of the tumor to the astrocyte, oligodendrocyte cell line or their precursor cells. In relation to that an interesting question arises- why the remaining tumors originating from glial cells other than astrocytic, such as ependymomas, lost their belonging to the group of glial tumors, or such as intracranial schwannomas, are not included in it at all.