A glioma is a brain tumor that may or may not be benign and malignant central nervous system neoplasms derived from the non-neuron glial cells (e.g., astrocytes, oligodendrocytes, and ependymocytes).  In the central nervous system, "benign" and "malignant" do not have the same connotation as elsewhere in the body. A malignant CNS tumor is highly invasive within the CNS but rarely crosses the blood-brain barrier for classic metastasis into other organ systems.
Astrocytes may give rise to astrocytomas or glioblastomas; they are less different diseases and more grading of histopathological diagnosis and aggressive behavior of the growth. Oligodendrocytes give rise to oligodendrogliomas and ependymocytes may undergo transformation to become ependyomas, choroid plexus neoplasms or colloid cysts of the third ventricle.  The terminology is part of the 1993 World Health Organization taxonomy. 
- Anonymous (2015), Glioma (English). Medical Subject Headings. U.S. National Library of Medicine.
- Escourolle et al., Manual of Basic Neuropathology, 2nd ed, p21, quoted by Medical Subject Headings
- Stephen B. Tatter (2006), The new WHO Classification of Tumors affecting the Central Nervous System, Neurosurgical Service, Massachusetts General Hospital