Brain cancers make up about 2 percent of all diagnosed cancers in the United States, according to the International RadioSurgery Association. Primary brain cancers develop from brain cells, as opposed to cancers that begin in other organs and subsequently spread to the brain. Gliomas are one type of primary brain cancer and arise from glial cells, which are cells that support the nerve cells of the brain. Just as there are several types of glial cells, there are several types of gliomas.
Astrocytoma
Astrocytomas are the most common type of glioma, according to the online medical library Merck Manuals. There are four subtypes of astrocytomas, which are classified based on severity and likelihood of spreading. The least malignant are low-grade astrocytomas (grade 1 or 2). Anaplastic astrocytomas are more malignant than low-grade astrocytomas and are grade 3, and usually develop in younger people. Glioblastomas are grade 4 and the most malignant astrocytoma. Glioblastomas usually develop in middle-aged or elderly people. The International RadioSurgery Association explains that low-grade tumors may or may not invade the surrounding healthy brain tissue, but are very slow growing and very unlikely to spread. Approximately 15 percent of primary brain tumors are grade 1 or 2 astrocytomas; only 4 percent of brain tumors are anaplastic astrocytomas; and 23 percent of primary brain tumors are glioblastomas.
Ependymoma
Ependymomas are a type of glioma that arise from the ependymal cells that line the ventricles (chambers) of the brain and the central portion of the spinal cord, according to the American Brain Tumor Association. Ependymomas are tumors that are red or gray in color, and sometimes contain cysts. Ependymomas are relatively rare among primary brain tumors, accounting for about only 2 to 3 percent of the total.
Oligodendrogliomas
The online medical library Merck Manuals reports that oligodendrogliomas are the most benign of all gliomas, meaning they are slow growing and unlikely to spread throughout the brain or to other tissues. Oligodendrogliomas develop in the cerebral cortex, which controls intelligence, sensation, and motor control. The International RadioSurgery Association adds that oligodendrogliomas are a rare type of brain cancer, accounting for only 3 percent of all primary brain tumors. About half of people with this type of brain tumor experience seizures as the first symptom of brain cancer.
