Types of Brain and Spinal Cord Tumors in Adults

Not all brain tumors are the same. Some grow slowly and stay contained, while others spread quickly into nearby tissue. Understanding the different types of tumors and how they are classified helps explain why treatment and prognosis can vary so widely.

Primary brain tumors vs. brain metastasis

There are two main types of brain and spinal cord tumors:

• Primary tumors start in the brain or spinal cord.
• Metastatic (secondary) tumors start in another part of the body (like the lung or breast) and then spread to the brain or spinal cord. These are more common than primary brain tumors in adults and are treated differently. To learn more, see Brain Metastases.

This information is about primary brain tumors and spinal cord tumors.

How doctors classify brain and spinal cord tumors

Doctors look at several features of brain or spinal cord tumors to help guide treatment and predict a person’s outlook:

Tumor type (based on the type of cell it starts in): Tumors can form in almost any type of tissue or cell in the brain or spinal cord. Each type of tumor tends to start in certain areas and to grow in certain ways. The most common types of brain and spinal cord tumors in adults are described below.

Tumor grade: This describes how the tumor cells look under the microscope and reflects how fast they are likely to grow and invade nearby tissues, based on a scale from 1 to 4:

• Lower grade (grade 1 or 2) tumors tend to grow more slowly and are less likely to grow into (invade or infiltrate) nearby tissues.
• Higher grade (grade 3 or 4) tumors tend to grow quickly and are more likely to grow into nearby tissues. They often need more intense treatment.

Gene changes in the tumor cells: As tumor cells grow, they can develop new changes, called mutations, in their genes (DNA). Even brain tumors of the same type can have different gene changes. For example, some tumors have mutations in one of the IDH genes (IDH1 or IDH2). Tumors with IDH mutations often grow more slowly and tend to have a better outlook than those without them. Other gene mutations can also be important for certain tumor types.

Tumor location: Where the tumor is in the brain or spinal cord can affect what symptoms it causes, as well as which treatments might be best. Even a small tumor in a sensitive or important area of the brain can cause serious problems, while a larger tumor in a less active area might cause fewer issues.

Gliomas

Gliomas are a large group of tumors that start in the brain’s support cells (called glial cells). About 3 out of 10 brain tumors are some type of glioma. Most faster-growing brain tumors are gliomas. There are 3 broad groups of gliomas:

• Astrocytomas
• Oligodendrogliomas
• Ependymomas

Each category has subtypes. For example, glioblastoma is the most common type of astrocytoma.

Astrocytomas

Astrocytomas start in glial cells called astrocytes. About 2 out of 10 brain tumors are astrocytomas. As with other types of brain tumors, astrocytomas are often grouped by grade.

Low-grade (grade 1 or 2) astrocytomas tend to grow slowly. These include:

• Non-infiltrating (grade 1) astrocytomas, which don’t usually grow into nearby tissues and tend to have a good outlook. Examples include pilocytic astrocytomas and subependymal giant cell astrocytomas (SEGAs). These tumors are more common in children than in adults.
• Grade 2 astrocytomas, such as diffuse astrocytomas and pleomorphic xanthoastrocytomas (PXAs). These tumors tend to be slow growing, but they can grow into nearby areas, which can make them harder to remove with surgery. They can become more aggressive and faster growing over time.

High-grade (grade 3 or 4) astrocytomas tend to grow quickly and spread into the surrounding normal brain tissue, which makes them hard to remove completely. These include:

• Grade 3 astrocytomas with IDH gene mutations (formerly known as anaplastic astrocytomas)
• Grade 4 astrocytomas with IDH gene mutations

Glioblastomas (GBMs) are grade 4 astrocytomas without an IDH mutation, and are the fastest growing. These tumors make up more than half of all gliomas and are the most common malignant brain tumors in adults.

For more on these tumors, see Glioblastoma.

Oligodendrogliomas

These tumors start in brain glial cells called oligodendrocytes. Most are grade 2 tumors that tend to grow slowly, but they can grow into (infiltrate) nearby brain tissue and be hard to remove completely with surgery. Like astrocytomas, they can become more aggressive over time. Aggressive (grade 3) forms are called anaplastic oligodendrogliomas.

Only about 1% to 2% of brain tumors are oligodendrogliomas.

Ependymomas

These tumors start in ependymal cells and typically grow in the ventricles (fluid-filled spaces of the brain) or spinal cord in adults. They can range from low-grade (grade 2) tumors to higher-grade (grade 3) tumors, which used to be called anaplastic ependymomas.

Only about 2% of brain tumors are ependymomas.

Ependymomas are more likely to spread along the cerebrospinal fluid (CSF) pathways than other gliomas. These tumors can block the flow of CSF from the ventricles, causing the ventricles to become very large, a condition called hydrocephalus.

Some ependymomas can be removed completely and cured by surgery, but this isn’t always possible because of the way they can spread. Spinal cord ependymomas have the greatest chance of being cured with surgery, but treatment can cause side effects related to nerve damage.

Meningiomas

Meningiomas begin in the meninges, the thin layers of tissue that cover the brain and spinal cord. These tumors account for about 1 out of 3 primary brain and spinal cord tumors. In adults, they are the most common primary tumors that affect the brain, although they are not technically brain tumors.

Meningiomas are more common in women and in older adults. Sometimes they run in families, especially in those with neurofibromatosis (schwannomatosis), a syndrome that leads to many benign nerve tumors.

Meningiomas are assigned a grade, based on how the cells look under the microscope:

• Grade 1 (benign) meningiomas are the most common and look the most like normal cells. Most can be removed with surgery, but some grow very close to vital structures in the brain or cranial nerves and can’t be cured by surgery alone.
• Grade 2 (atypical or invasive) meningiomas usually look slightly more abnormal. They can grow directly into nearby brain tissue or bone and are more likely to come back (recur) after surgery.
• Grade 3 (anaplastic or malignant) meningiomas are the least common and look the most abnormal. 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.

For more on these tumors, see Meningioma.

Schwannomas (neurilemmomas)

Schwannomas develop from Schwann cells, which surround and insulate cranial nerves and some other nerves. They make up about 5% to 10% of all brain and spinal cord tumors.

Schwannomas are almost always benign (grade 1) tumors. They can arise from any cranial nerve.

• When they form on the cranial nerve responsible for hearing and balance, they are called vestibular schwannomas or acoustic neuromas. These tumors can cause hearing loss, ringing in the ears, and balance issues.
• These tumors can also form on the spinal nerves after they branch out from the spinal cord. When this happens, they can press on the spinal cord or nearby nerves, leading to symptoms such as weakness, numbness or tingling, and problems with bowel or bladder control.

Tumors that are more common in children

Some types of brain tumors are more common in children, but they still sometimes affect adults.

• Medulloblastomas develop from neuroectodermal cells (early nerve cells) in the back part of the brain called the cerebellum. They are part of a class of tumors called embryonal tumors that can also start in other parts of the brain or spinal cord. Medulloblastomas are fast-growing (grade 4) tumors and often spread throughout the CSF pathways, but they can be treated with surgery, radiation therapy, and chemotherapy.
• Craniopharyngiomas are slow-growing (grade 1) tumors that 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 affect vision. Their tendency to stick to these important structures can make them hard to remove completely without damaging vision or hormone balance.
• Gangliogliomas contain both nerve cells (neurons) and glial cells. These tumors are rare in adults. They are typically slow-growing (grade 1) tumors and can usually be cured by surgery, alone or combined with radiation therapy.

Since these tumors are more common in children, see Brain Tumors in Children for more details.

Other tumors that can start in or near the brain

Chordomas

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 damage 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 on chordomas, see Bone Cancer.

Primary CNS lymphomas

Lymphomas are cancers that start in white blood cells called lymphocytes (one of the main cell types of the immune system). Most lymphomas start in other parts of the body, but some start in the CNS, and are called primary CNS lymphomas.

These lymphomas are more common in people with immune system problems, such as HIV infection or AIDS. Because of better treatments for AIDS, primary CNS lymphomas have become less common over time. They account for about 2% of primary brain tumors.

These lymphomas often grow quickly and can be hard to treat. But recent advances in treatment have improved the outlook for people with these cancers.

For more on primary CNS lymphomas (including treatment), see Non-Hodgkin Lymphoma.

Pituitary tumors

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 pituitary hormone.

To learn more, see Pituitary Tumors.