Oligodendrogliomas: oligodendrocytes
Brainstem glioma: develop in the brain stem
Optic nerve glioma: develop in or around the optic nerve
Mixed gliomas, such as oligoastrocytomas, contain cells from different types of glia

By grade
Gliomas are further categorized according to their grade, which is determined by pathologic evaluation of the tumor. The neuropathological evaluation and diagnostics of brain tumor specimens is performed according to WHO Classification of Tumours of the Central Nervous System. Biologically benign gliomas [WHO grade I] are comparatively low risk and can be removed surgically depending on their location 
Low-grade gliomas [WHO grade II] are well-differentiated (not anaplastic);  these tend to exhibit  benign tendencies and portend a better prognosis for the patient. However, they have a uniform rate of recurrence and increase in grade over time so should be classified as malignant. High-grade [WHO grades III–IV] gliomas are undifferentiated or anaplastic; these are malignant and carry a worse prognosis.Of numerous grading systems in use, the most common is the World Health Organization (WHO) grading system for astrocytoma, under which tumors are graded from I (least advanced disease—best prognosis) to IV (most advanced disease—worst prognosis). By location
Gliomas can be classified according to whether they are above or below a membrane in the brain called the tentorium. The tentorium separates the cerebrum (above) from the cerebellum (below). The supratentorial is above the tentorium, in the cerebrum, and mostly found in adults (70%). The infratentorial is below the tentorium, in the cerebellum, and mostly found in children (70%). The pontine tumors are located in the pons of the brainstem.
As a rule, high-grade gliomas almost always grow back even after complete surgical excision, so are commonly called recurrent cancer of the brain.Conversely, low-grade gliomas grow slowly, often over many years, and can be followed without treatment unless they grow and cause symptoms.Several acquired (not inherited) genetic mutations have been found in gliomas. Tumor suppressor protein 53 (p53) is mutated early in the disease. p53 is the "guardian of the genome", which, during DNA and cell duplication, makes sure the DNA is copied correctly and destroys the cell (apoptosis) if the DNA is mutated and cannot be fixed. When p53 itself is mutated, other mutations can survive. Phosphatase and tensin homolog (PTEN), another tumor suppressor gene, is itself lost or mutated. Epidermal growth factor receptor, a growth factor that normally stimulates cells to divide, is amplified and stimulates cells to divide too much. Together, these mutations lead to cells dividing uncontrollably, a hallmark of cancer. In 2009, mutations in IDH1 and IDH2 were found to be part of the mechanism and associated with a less favorable prognosis. Diagnosis
Classification
Gliomas are classified by cell type, by grade, and by location. By type of cell
Gliomas are named according to the specific type of cell with which they share histological features, but not necessarily from which they originate. The main types of glioma are:
Ependymomas: ependymal cells
Astrocytomas: astrocytes (glioblastoma multiforme is a malignant astrocytoma and the most common primary brain tumor among adults).