About half of all primary brain tumours and about one-fifth of all primary spinal cord tumours are gliomas, meaning they grow from glial cells. These usually occur in the cerebral hemisphere, but may also strike other areas such as the optic nerve, the brain stem and the cerebellum. Gliomas are classified into several groups because there are different types of glial cells. Astrocytoma Astrocytomas, the most common type of glioma, are also the most common type of primary brain tumour. They develop from star shaped glial cells called astrocytes.
Treatment usually requires surgery, radiation therapy and sometimes chemotherapy.
Decisions about how to treat each particular astrocytoma are based mainly on the tumour's grade the degree of anaplasia the pathologist sees when tissue from a biopsy specimen of the astrocytoma is examined under a microscope. Anaplasia is the term used to describe the characteristic pattern in which tumour cells grow without form, structure or orientation to one another. An astrocytoma is assigned a grade according to its degree of anaplasia. The degree of anaplasia reflects its potential for growth. The most rapidly growing astrocytomas have the greatest degree of anaplasia, are the most anaplastic and are therefore the most malignant.