Types of brain and spinal cord tumors in adults
Tumors that start in the brain (primary brain tumors) are not the same as tumors that start in other organs, such as the lung or breast, and then spread to the brain (metastatic or secondary brain tumors). In adults, metastatic tumors to the brain are actually more common than primary brain tumors. These tumors are not treated the same way. For example, breast or lung cancers that spread to the brain are treated differently from tumors that start in the brain.
This document is only about primary brain and spinal cord tumors, not those that have spread to the brain and spinal cord from elsewhere in the body.
Unlike cancers that start in other parts of the body, tumors that start in the brain or spinal cord rarely spread to distant organs. Even so, tumors of the brain or spinal cord are rarely considered benign (non-cancerous). They can still cause damage by growing and spreading into nearby areas, where they can destroy normal brain tissue. And unless they are completely removed or destroyed, most brain or spinal cord tumors will continue to grow and eventually be life-threatening.
Primary brain tumors can start in almost any type of tissue or cell in the brain or spinal cord. Some tumors have a mixture of cell types. Tumors in different areas of the central nervous system may be treated differently and have a different prognosis (outlook).
Gliomas are not a specific type of brain tumor. Glioma is a general term for a group of tumors that start in glial cells. A number of tumors can be considered gliomas, including glioblastoma (also known as glioblastoma multiforme), astrocytomas, oligodendrogliomas, and ependymomas. About 3 out of 10 of all brain tumors are gliomas. Most fast-growing brain tumors are gliomas.
Astrocytomas are tumors that start in glial cells called astrocytes. About 2 out of 10 brain tumors are astrocytomas.
Most astrocytomas can spread widely throughout the brain and blend with the normal brain tissue, which can make them very hard to remove by surgery. Sometimes they spread along the cerebrospinal fluid (CSF) pathways. It is very rare for them to spread outside of the brain or spinal cord.
Astrocytomas are often classified as high grade, intermediate grade, or low grade, based largely on how the cells look under the microscope.
- High grade astrocytomas, known as glioblastomas (or glioblastoma multiforme), are the fastest growing. These tumors make up about two-thirds of astrocytomas and are the most common malignant brain tumors in adults.
- Intermediate-grade astrocytomas, or anaplastic astrocytomas, grow at a moderate rate.
- Low-grade (diffuse) astrocytomas tend to be slow growing, but they can become more aggressive and fast growing over time.
- Some low-grade types called non-infiltrating astrocytomas do not usually grow into nearby tissues and tend to have a good prognosis. These include pilocytic astrocytomas and dysembryoplastic neuroepithelial tumors (DNETs). They are more common in children than in adults.
These tumors start in brain glial cells called oligodendrocytes. These tumors tend to grow slowly, but like astrocytomas, most of them can grow into (infiltrate) nearby brain tissue and cannot be removed completely by surgery. Oligodendrogliomas sometimes spread along the CSF pathways but rarely spread outside the brain or spinal cord. As with astrocytomas, they can become more aggressive over time. Very aggressive forms of these tumors are known as anaplastic oligodendrogliomas. Only about 2% of brain tumors are oligodendrogliomas.
These tumors arise from ependymal cells, which line the ventricles. They can range from fairly low-grade (less aggressive) tumors to higher grade ones, which are called anaplastic ependymomas. Only about 2% of brain tumors are ependymomas.
Ependymomas are more likely to spread along the CSF pathways than other gliomas but do not spread outside the brain or spinal cord. Ependymomas may block the exit of CSF from the ventricles, causing the ventricles to become very large – a condition called hydrocephalus.
Unlike astrocytomas and oligodendrogliomas, ependymomas usually do not grow into normal brain tissue. As a result, some (but not all) ependymomas can be removed completely and cured by surgery. But because they can spread along ependymal surfaces and CSF pathways, treating them can sometimes be difficult. Spinal cord ependymomas have the greatest chance of being cured with surgery, but treatment can cause side effects related to nerve damage.
These tumors contain more than one cell type. For example, oligoastrocytomas have some of the same types of cells as both oligodendrogliomas and astrocytomas. Treatment is typically based on the fastest growing component of the tumor.
Meningiomas begin in the meninges, the layers of tissue that surround the outer part of the brain and spinal cord. Meningiomas account for about 1 out of 3 primary brain and spinal cord tumors. They are the most common brain tumors in adults (although strictly speaking, they are not actually brain tumors).
The risk of these tumors increases with age. They occur about twice as often in women. Sometimes these tumors run in families, especially in those with neurofibromatosis, a syndrome in which people develop many benign tumors of nerve tissue.
Meningiomas are often assigned a grade, based on how the cells look under the microscope.
- Grade I (benign) tumors have cells that look the most like normal cells. They make up about 80% of meningiomas. Most of these can be cured by surgery, but some grow very close to vital structures in the brain or cranial nerves and cannot be cured by surgery alone.
- Grade II (atypical or invasive) meningiomas usually have cells that look slightly more abnormal. About 15% to 20% of meningiomas are grade II. They can grow directly into nearby brain tissue and bone and are more likely to come back (recur) after surgery.
- Grade III (anaplastic) meningiomas have cells that look the most abnormal. They make up only about 1% to 3% of meningiomas. They tend to grow quickly, can grow into nearby brain tissue and bone, and are the most likely to come back after treatment. Some may even spread to other parts of the body.
Medulloblastomas develop from neuroectodermal cells (primitive nerve cells) in the cerebellum. They are fast-growing tumors and often spread throughout the CSF pathways, but they can be treated by surgery, radiation therapy, and chemotherapy.
Medulloblastomas occur much more often in children than in adults. They are part of a class of tumors called primitive neuroectodermal tumors (PNETs) that can also start in other parts of the central nervous system. They are discussed in more detail in our document Brain and Spinal Cord Tumors in Children.
Schwannomas develop from Schwann cells, which surround and insulate cranial nerves and other nerves. They make up about 8% of all CNS tumors.
Schwannomas are almost always benign tumors. They can arise from any cranial nerve. When they form on the cranial nerve responsible for hearing and balance near the cerebellum they are called vestibular schwannomas or acoustic neuromas. They can also start on spinal nerves after the point where they have left the spinal cord. When this happens, they can press on the spinal cord, causing weakness, sensory loss, and bowel and bladder problems.
These slow-growing tumors start above the pituitary gland but below the brain itself. They may press on the pituitary gland and the hypothalamus, causing hormone problems. Because they start very close to the optic nerves, they can also cause vision problems. Their tendency to stick to these important structures can make them hard to remove completely without damaging vision or hormone balance. Craniopharyngiomas are more common in children, but they are sometimes seen in adults.
Other tumors that can start in or near the brain
These rare tumors start in the bone at the base of the skull or at the lower end of the spine. Chordomas don’t start in the central nervous system, but they can injure the nearby brain or spinal cord by pressing on it.
These tumors are treated with surgery if possible, often followed by radiation therapy, but they tend to come back in the same area after treatment, causing more damage. They usually do not spread to other organs. For more information on chordomas, see our document Bone Cancer.
Lymphomas are cancers that start in cells called lymphocytes (one of the main cell types of the immune system). Most lymphomas start in other parts of the body, but some may start in the CNS. These lymphomas are more common in people with immune system problems, such as those infected with HIV, the virus that causes AIDS. Because of new treatments for AIDS, CNS lymphomas have become less common in recent years.
These lymphomas often grow quickly and can be hard to treat. Recent advances in chemotherapy, however, have improved the outlook for people with these cancers. For more information on CNS lymphomas (including treatment), see our document Non-Hodgkin Lymphoma.
Tumors that start in the pituitary gland are almost always benign (non-cancerous). But they can still cause problems if they grow large enough to press on nearby structures or if they make too much of any kind of hormone. For more information, see our document Pituitary Tumors.
Last Medical Review: 03/05/2014
Last Revised: 03/05/2014