These cancers arise from the glial cells that form the supporting tissue in the brain. The most common glial cells are astrocytes (star-shaped cells), oligodendrocytes and ependymal cells. The glial tissue, unlike nerve cells, can reproduce. The largest percentage of brain tumors originates in glial tissue.
Astrocytomas are the most common form of glioma and the most common type of primary brain cancer. These cancers can develop in any part of the central nervous system: the brain, brain stem or spinal cord.
An astrocytoma brain tumor may be further classified into one of the grades shown below. A grade is a determination of how well differentiated the tumor cells look when viewed by a pathologist under a microscope. Cells that are well differentiated mean that they have clear boundaries and structure. They are the least malignant form of cancer. Cells that are not well-differentiated do not have distinct boundaries and are considered to be more aggressive and thus more malignant.
These tumors are slow growing and do not usually invade tissue around them. The cells of these tumors are well differentiated, meaning that their structure is well defined when viewed under a microscope. They are considered a low grade of cancer and offer the best chance to be completely removed during surgery. However, if the tumor is in an inaccessible part of the brain, it can be impossible to remove completely.
These tumors are referred to as grade III astrocytomas. Their cell structure is less well-differentiated and, as a result, the tumors are more aggressive and more malignant.
These tumors are referred to as high grade or grade IV astrocytomas. They are a highly aggressive, highly malignant form of cancer that spreads rapidly into adjoining tissue in the brain. When viewed under a microscope, the cells of this tumor have lost their structure and mitotic figures (dividing cells) are often seen. Other features required to make a diagnosis of GBM are necrotic tissue and newly formed blood vessels within the tumor. Glioblastoma multiforme is the most common type of astrocytoma brain cancer.
These tumors are located in the portion of the brain that connects to the spinal cord. Because they are in a vital area of the brain, they are rarely surgically removable and are much more common in children than adults.
This cancer occurs in the part of the brain called the cerebellum, located above the back of the neck near the brain stem. It is a slow-growing form of cancer that usually does not spread to other parts of the brain. Cystic cerebellar astrocytomas in children are potentially curable by surgery, but diffuse types of tumors in adults are not.
These tumors arise in the cells that line the hollow spaces in the brain, called ventricles, which contain the spinal fluid. The level of aggressiveness of this type of cancer will depend on what the cells look like under a microscope and will be classified as well-differentiated ependymoma, anaplastic ependymoma or ependymoblastoma.
These tumors originate in the cells called oligodendrocytes, which support and feed the cells that transmit nerve impulses. The tumor grade will depend on what the cells look like under a microscope, which will establish its level of malignancy. Oligodendroglial tumors can be either well differentiated or anaplastic. This is a special subtype of astrocytoma which usually responds to chemotherapy, especially when chromosomal tests (such as loss of chromosomes IP + 19Q) are favorable. This testing can be done on surgically obtained brain samples.
These brain tumors consist of more than one type of cell: astrocytes, ependymal cells or oligodendrocytes.
This tumor originates in the lower portion of the brain and may spread to the spine. It is more common in children and young adults.
This tumor originates in or forms around the pineal gland located deep within the brain. The tumor may be either slow growing (pineocytoma) or fast growing (pineoblastoma).
These tumors arise in the sex cells in the brain. Different kinds of germ cell tumors include germinomas, embryonal carcinomas, choriocarcinomas and teratomas. These tumors may be either slow or fast growing.
These tumors occur near the pituitary gland, located just below the optic nerve and are usually slow growing.
These tumors occur in the membranes that cover the brain and spinal cord, pushing and disturbing nervous tissue. These are more properly considered meningeal (membrane) tumors, and not tumors which arise within the brain.
This rare form of meningioma spreads quickly, sometimes growing through the bone of the skull.
These tumors arise in the choroid plexus tissue located in the spaces in the brain called ventricles. Choroid plexus tissue makes fluid that fills the ventricles and surrounds the brain and spinal cord. These tumors can grow slowly (choroid plexus papilloma) or quickly (anaplastic choroid plexus papilloma). The quickly growing form can spread to other parts of the brain and to the spinal cord.
Recurrent brain tumors are cancers that come back after treatment.