The possibility of being diagnosed with a brain tumor can be a shocking and life-changing event. If your doctor suspects a brain tumor, it is important to seek out doctors who specialize in diagnosing and treating brain tumors. The brain is a complex and vital organ, and treatment often causes life-long changes. Research about brain tumor treatment is ongoing, so it is important to get updated medical information about treatment options about the specific type of brain tumor and to get specialists’ opinions about your treatment plan.
About the brain and central nervous system
The brain and spinal column make up the central nervous system (CNS), where all vital functions are controlled. These functions include thought, speech, and body movements. This means that when a tumor grows in the CNS, it can affect a person’s thought processes or the way they talk or move.
Anatomy of the brain
The brain is made up of 3 main parts: the cerebrum, the cerebellum, and the brain stem. The meninges, which surround the brain, are also considered part of the brain.
- The cerebrum.This is the largest part of the brain. It contains 2 cerebral hemispheres on either side of the brain that each control the opposite side of the body. It is divided into 4 lobes where specific functions occur:
- The frontal lobe controls reasoning, emotions, problem-solving, expressive speech, and movement.
- The parietal lobe controls the sensations of touch, such as pressure, pain, and temperature. It also controls parts of speech, visual-spatial orientation, and calculation.
- The temporal lobe controls memory, special senses such as hearing, and the ability to understand spoken or written words.
- The occipital lobe controls vision.
- The cerebellum. The cerebellum is located at the back part of the brain below the cerebrum. It is responsible for coordination and balance, and it controls functions on the same side of the body.
- The brain stem. This is the portion of the brain that connects to the spinal cord and the cerebellum. It controls involuntary functions essential for life, such as the beating of the heart and breathing. Messages for the functions controlled by the cerebrum and cerebellum travel through the brain stem to the body.
- The meninges. These are the membranes that surround and protect the brain and spinal cord. There are 3 meningeal layers, called the dura mater, arachnoid, and pia mater. The cerebrospinal fluid (CSF) is made near the center of the brain, in the lateral ventricles. CSF circulates around the brain and spinal cord between the arachnoid and pia layers.
About primary brain tumors
A primary brain tumor is a tumor that starts in the brain. A primary brain tumor is often described as either “low grade” or “high grade.” A low-grade tumor generally grows slowly, but it can turn into a high-grade tumor. A high-grade tumor is more likely to grow faster.
In adults, a secondary brain tumor, also called a brain metastasis, is much more common than a primary brain tumor.
About secondary brain tumors
A secondary brain tumor, or brain metastasis, is a cancerous tumor that started in another part of the body, such as the breast, lung, or colon, and then spread to the brain. A secondary brain tumor may also be called metastatic cancer. For instance, lung cancer that has spread to the brain may be called metastatic lung cancer.
If cancer spreads to the meninges and CSF, it is called leptomeningeal metastases or neoplastic meningitis. This condition occurs more commonly in people with leukemia, lymphoma, melanoma, breast cancer, or lung cancer.
The rest of this guide mainly covers primary brain tumors in adults, while providing some information on brain metastases. To learn more detailed information about cancer that started elsewhere in the body and spread to the brain, read about that specific type of cancer. Learn about brain tumors in children in a different guide on this same website.
Types of primary brain tumors in adults
There are many types of primary brain tumors. Some cannot be assigned an exact type because the tumor’s location makes it too difficult to remove for full testing.
Descriptions of more common brain tumor types in adults are described below, divided into glioma and non-glioma tumor types.
As a group, gliomas are one of the most common types of brain tumors. A glioma is a tumor that grows from a glial cell. A glial cell is a type of supportive cell in the brain. The main types of supportive cells in the brain include astrocytes, oligodendrocytes, and ependymal cells. Gliomas may be considered astrocytomas, oligodendrogliomas, or ependymomas. Gliomas are assigned a grade, which is an indication of how aggressive a tumor is likely to be. A higher grade is usually more aggressive and more likely to grow quickly. However, doctors are moving toward using tumor genetics to better classify gliomas. This is discussed later in this guide.
Currently, the types of gliomas include:
- Astrocytoma. Astrocytoma is the most common type of glioma and begins in cells called astrocytes in the cerebrum or cerebellum. There are 4 grades of astrocytoma.
- Grade I or pilocytic astrocytoma is a slow–growing tumor that is most often benign and rarely spreads into nearby tissue. Astrocytoma in children is more common than astrocytoma in adults.
- Grade II or low–grade diffuse astrocytoma is a slow–growing tumor that can often spread into nearby tissue and can become a higher grade.
- Grade III or anaplastic astrocytoma is a cancerous tumor that can quickly grow and spread to nearby tissues.
- Grade IV or glioblastoma is a very aggressive form of astrocytoma.
- Oligodendroglioma. Oligodendroglioma is a tumor that develops from cells called oligodendrocytes. These cells are responsible for making myelin. Myelin surrounds the nerves and is rich in protein and fatty substances called lipids. They are subclassified as either oligodendroglioma, which is considered low grade, or anaplastic oligodendroglioma.
- Ependymoma. Ependymoma commonly begins in the passageways in the brain where CSF is made and stored. In adults, they occur more often in the spine and can also be of the myxopapillary subtype. Learn about ependymoma in children.
- Brain stem glioma. A brain stem glioma begins in the glial cells in the brain stem. Learn about brain stem glioma in children.
The following section covers non–glioma tumors. These are tumors that arise from cells in the brain that are not glial cells. Types of non–glioma tumors include:
- Meningioma. Meningioma is the most common primary brain tumor. It begins in the meninges and is most often noncancerous. Meningioma can cause serious symptoms if it grows and presses on the brain or spinal cord or grows into the brain tissue. Learn more about meningioma.
- Pineal gland and pituitary gland tumors. These are tumors that start in the pineal gland and pituitary gland.
- Primary CNS lymphoma. This is a form of lymphoma. Lymphoma is a cancer that begins in the lymphatic system. Primary CNS lymphoma starts in the brain and can spread to the spinal fluid and eyes.
- Medulloblastoma. Medulloblastoma is thought to start from a specific type of cell in the cerebellum. These cells are called cerebellar granule progenitor cells. It is most common in children and is usually cancerous, often spreading throughout the CNS. Similar tumors can start in other parts of the brain and are called primitive neuroectodermal tumors (PNET). Learn about medulloblastoma in children.
- Craniopharyngioma. Craniopharyngioma is a benign tumor that begins near the pituitary gland located near the base of the brain. These tumors are rare. Learn about craniopharyngioma in children.
- Schwannoma. Schwannoma is a rare tumor that begins in the nerve sheath, or the lining of the nerves. It may often occur in the vestibular nerve, which is a nerve in the inner ear that helps control balance. It is typically noncancerous.