About 17,000 people are diagnosed with cancer that began in or next to the brain every year in the United States. These are called primary brain cancers. Another 100,000 people are diagnosed with cancer in the brain or spinal cord that spread (metastasized) from another place in the body. These are called secondary brain cancers.
Most types of brain tumors are slightly more common in men than women. Meningiomas are more common in women.
Growth Causes Problems
Some brain tumors grow slowly and may become quite large before causing symptoms. Others may grow quickly and cause a sudden onset of symptoms. While most types of brain cancer may spread within the brain, few spread beyond the brain. Because the skull is rigid, providing no room for the tumor to expand, brain tumors may press on parts of the brain that control movement, speech, sight or other vital functions.
Even when brain tumors are benign (not cancer), they can cause serious problems. Although non-cancerous brain tumors usually grow slower than cancerous brain tumors, they may damage and press against normal brain tissue or the spine as they grow.
Brain Has Crucial Roles
Emotions, thought, speech, vision, hearing, movement and many more important parts of everyday life begin in the brain. The brain sends messages throughout the body via the spinal cord and cranial nerves in the head. The network of the brain and spinal cord is called the central nervous system (CNS). Tumors can develop in the spinal cord and cranial nerves.
The hard, bony skull protects the brain, and the bones (vertebrae) of the spine protect the spinal cord. A liquid called cerebrospinal fluid surrounds both the brain and the spinal cord.
The brain has four main parts:
Cerebrum: The outer and largest part of the brain. The cerebrum has two halves that are called hemispheres. It is responsible for:
- Movement of muscles
- Senses of seeing, hearing, smelling, touch
- Perception of pain
Basal ganglia: These are found deeper inside the brain. They play a part in muscle movement.
Cerebellum: This section is at the back of the brain. It helps control and coordinate movement, such as walking and swallowing.
Brain stem: The brain stem is at the base of the brain. Its nerve fibers carry messages between the cerebrum and the rest of the body. This small area is very important and even plays a part in breathing and heartbeat.
Brain Tumor Types
Brain tumors are classified by the types of cells within the tumor. Each type of brain tumor grows and is treated in a different way.
The main types of brain tumors are as follows. The type of cells where they begin are in parentheses.
- Adenoma (pituitary gland)
- Chordoma (skull and spine)
- Craniopharyngioma (pituitary gland)
- Dermoid cysts and epidermoid tumors
- Germ cell tumors, including germinomas (near the pineal gland)
- Gliomas: This is the main group of brain tumors, occurring in 65% of cases. It includes:
- Glioblastoma multiforme (glial cells and oligodendrocytes), the type of brain cancer found most often in adults
- Astrocytoma (glial cells of tissue that supports nerve cells)
- Oligodendroglioma (oligodendrocytes in the myelin sheath around nerve fibers in the brain)
- Ependymoma (the ventricles in tissue lining the spaces within the brain)
- Hemangioblastoma (cells that develop into blood vessels)
- Medulloblastoma (cerebellum)
- Meningioma (meninges, the layers of tissue covering the brain)
- Osteoma and osteosarcoma (bones of the skull)
- Pinealoma (pineal gland)
- Pituitary adenoma (pituitary gland)
- Sarcoma (connective tissue)
Cancers that metastasize (spread) to the brain are called metastases. They may grow in one or several parts of the brain. Many types of cancer can spread to the brain. The main types are breast cancer, lung cancer, gastrointestinal cancers, malignant melanoma, leukemia and lymphoma.
Lymphomas of the brain often are found in people who have AIDS. For unknown reasons, they are increasingly being found in people with normal immune systems.
Brain Tumor Risk Factors
Anything that increases your chance of getting a brain tumor is a risk factor. While no definite risk factors have been found for brain tumors, some factors may put you at increased risk, including:
- Radiation exposure
- Family history of certain conditions including:
- Immune system disorders, including AIDS and lymphoma
Research is ongoing into the causes and risk factors of brain tumors. Many possibilities are being studied, including genetics and environmental exposure to certain chemicals.
Some types of brain tumors may be passed down from one generation to the next. Genetic counseling may be right for you. Learn more about the risk to you and your family on our genetic testing page.