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 primary brain cancer may spread within the brain, it is rare for a primary brain tumor to spread outside 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 spinal cord as they grow, potentially causing symptoms.
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. Each hemisphere has four lobes: frontal, parietal, temporal and occipital. The cerebrum 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.
Brainstem: 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 tumors are classified by the types of cells within the tumor. Each type of brain tumor grows and is treated in a different way.
Craniopharyngiomas are non-cancerous, slow growing tumors located near the pituitary gland. Craniopharyngioma appears primarily in children and middle-age adults. The tumor itself can be part solid and part fluid-filled cyst. Symptoms can include vision changes and slow growth caused by the tumor’s impact on the pituitary gland. These tumors primarily require treatment with specialized surgery and possibly radiation after surgery.
Dermoid cysts and epidermoid tumors are benign growths that arise from epithelial cells, which form the outer layer of the body and line certain organs and glands. They can develop in various parts of the body, including the central nervous system. Both are slow growing, and are often not noticed for decades. They are treated by surgical removal.
Gliomas are a class of primary brain tumors. They are some of the fastest-growing brain tumors. The different types of gliomas include:
- Astrocytoma: Astrocytomas spread throughout the brain and mix with healthy tissue, making them difficult to treat. There are several types of astrocytoma:
- Low-grade astrocytomas: These include grade I pilocytic astrocytoma and grade II diffuse astrocytoma. Grade I astrocytomas are rarely seen in adults.
- Anaplastic astrocytoma: Grade III astrocytomas are known as anaplastic astrocytoma. These tumors are aggressive, high-grade cancers.
- Glioblastoma: Grade IV astrocytomas are called glioblastoma or GBM. Glioblastoma is the most common malignant (cancerous) adult brain tumor and one of the fastest-growing tumors of the central nervous system.
- Ependymoma: Ependymomas arise from ependymal cells, which line the ventricles of the brain and the center of the spinal cord. The ventricles are chambers in the brain that produce and transport cerebrospinal fluid, which surrounds and protects the brain. Ependymomas may be found in the brain or the spine. Ependymomas are more commonly seen in children and are rare in adults.
- Oligodendroglioma: Oligodendroglioma is generally slow growing. It can be diagnosed as a grade II or grade III tumor.
These slow-growing tumors develop from the cells of blood vessels. A hemangioblastoma typically forms in the brainstem and cerebellum, but can appear in other locations, including the retina. About a quarter of cases are associated with von Hippel Lindau disease, a genetic condition that is tied to the development of multiple types of tumors and cancers.
Medulloblastoma is the most common pediatric malignant brain tumor, with about 500 children diagnosed a year in the United States. In adults, medulloblastoma is a rare tumor, with about 200 diagnoses each year. Learn more on our medulloblastoma page.
Meningioma is the most common primary brain tumor. These tumors develop from cells in the meninges, the protective layer of tissue surrounding the brain and spinal cord. Most are benign and slow growing. Some, though, are malignant and aggressive. Surgery is usually the first treatment for meningiomas that grow and cause symptoms.
The pineal gland is located deep in the brain and makes the sleep regulating hormone melatonin. Tumors of the pineal gland can be benign or malignant. Pineal tumors include pineocytoma and pineoblastoma.
Pituitary tumors, also called pituitary adenomas, are usually benign (non-cancerous) growths on the pituitary gland. The pituitary gland is a key part of the endocrine system, which controls the growth and development. Learn more on our pituitary tumor page.
Sarcomas are broad category of tumors that form in bones and the body’s soft tissues, including cartilage, fat, and muscle. Soft tissue sarcomas are more common than bone sarcomas. Bone sarcoma types include Ewing’s sarcoma and osteosarcoma. Some gliomas have sarcoma-like characteristics and are called gliosarcomas. Gliosarcomas behave aggressively similar to glioblastomas.
Sarcomas may also be found in the spine or skull base, including chordoma. Chordomas are rare sarcoma tumors that grow in the base of the skull and bones of the spine. Doctors believe they develop from the leftover cells that served as the framework for the skull base and spine when the patient was a developing embryo. When chordomas form in the skull, they can push into the brain and cause many of the same symptoms as brain tumors, including headaches, dizziness and confusion. Chordomas can involve multiple critical nerves and arteries, making them difficult to treat. Treatment may require the use of specialized surgery, radiation therapy and/or chemotherapy.
Primary Brain Tumor Risk Factors
Anything that increases your chance of getting a brain tumor is a risk factor. Research is ongoing into the causes and risk factors of brain tumors. While no definite risk factors have been found for brain tumors, some factors may put you at increased risk, including:
- Prior radiation exposure to the brain, often as treatment for another cancer
- Family history of certain conditions including:
Some types of brain tumors may be passed down from one generation to the next, if you have a family history of the conditions listed above. Genetic counseling may be right for you. Learn more about the risk to you and your family on our genetic testing page.