Approximately half of all primary brain tumours and one-fifth of all primary spinal cord tumours are gliomas, meaning they grow from glial cells. In the brain, gliomas usually occur in the cerebral hemispheres but may also develop in other areas, including the optic nerve, the brain stem and the cerebellum. (Please refer to the diagram below). Gliomas are classified into several groups because there are different kinds of glial cells.

Following are the different glioma classifications:

A. WELL-DIFFERENTIATED (OR LOW-GRADE) ASTROCYTOMAS
Well-differentiated astrocytomas, also known as low-grade astrocytomas or grade I or II astrocytomas, are tumours that contain cells that are relatively normal and less malignant than the other two grades. They grow slowly and may sometimes be completely removed through surgery. However, even well-differentiated astrocytomas can be life-threatening if they are present in areas of the brain that are not easily accessible. In some cases, well-differentiated astrocytomas can also progress or recur into higher-grade tumours.

B. ANAPLASTIC (OR HIGH-GRADE) ASTROCYTOMAS
Anaplastic astrocytomas, also called high-grade or grade III astrocytomas, grow more rapidly than lower-grade astrocytomas and contain cells with malignant traits. Surgery followed by radiation therapy, and often chemotherapy, is used to treat anaplastic astrocytomas. There are many clinical trials looking into new treatments for anaplastic astrocytomas.

C. GLIOBLASTOMA MULTIFORME (GBM)
GBM tumours, also called high-grade or grade IV astrocytomas, grow rapidly, invade nearby tissue and contain cells that are very malignant. GBM is among the most common and devastating type of primary brain tumour that affects adults, and in some cases children. Doctors usually treat glioblastomas with surgery followed by radiation therapy and often chemotherapy, or a combination of these therapies.