About half of all primary brain tumors and about one-fifth of all primary spinal cord tumors are gliomas, meaning that they grow from glial cells. Within the brain, gliomas usually occur in the cerebral hemispheres but may also strike other areas, especially the optic nerve, the brain stem and, particularly among children, the cerebellum. Gliomas are classified into several groups because there are different kinds of glial cells. Astrocytoma Astrocytomas, the most common type of glioma, are also the most common type of primary brain tumor. They develop from star-shaped glial cells called astrocytes.
Treatment usually includes surgery, radiation therapy and sometimes chemotherapy.
Decisions about how to treat an astrocytoma are based mainly on the tumor'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 tumor 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 the tumor's potential for growth. The most rapidly growing astrocytomas have the greatest degree of anaplasia, are the most anaplastic and are therefore the most malignant.