The most common types of brain cancers are gliomas and meningiomas.
Gliomas are cancers that grow from glia cells or glial cells, which are supportive cells that hold neurons in place. Glial cells provide nutrition and form myelin, which is a covering for nerve cells. Glial cells include:
- Ependymal cells.
About half of all primary brain cancers are from glial cells. About one-fifth of all primary spinal cord cancers are from glial cells. Gliomas occur more often in men than women.
Meningiomas are cancers that grow from the brain covering (meninges). About 15 to 25 percent of all primary brain cancers are meningiomas. Meningiomas occur more often in women than men.
Primary Cancers from Glial Cells (Gliomas)
Astrocytomas start from brain cells called astrocytes (star-shaped cells). They are the most common type of glioma, slow-growing, and can be anywhere in the brain, but are most often in the cerebrum. If found early, they can often be surgically removed.
[Astrocytoma image reprinted by permission from Macmillan Publishers Ltd: Nature Publishing Group, Nature Reviews Cancer, (The Molecular and Genetic Basis of Neurological Tumours), copyright 2002.]
There are different grades of astrocytomas:
- Pilocytic astrocytoma (Grade I) which grow slowly and usually do not grow into the surrounding tissues.
- Low-grade (glioma) astrocytoma (Grade II) is slow growing, but grows more quickly than pilocytic astrocytomas and grow into surrounding tissues.
- Anaplastic astrocytoma (Grade III) cells look very different from normal cells. They grow faster than low-grade astrocytomas and are also called high-grade astrocytomas or gliomas, which often recur.
- Glioblastoma multiforme (Grade IV) is the most common brain cancer accounting for over 50 percent of all brain cancers. They grow quickly and faster than low-grade astrocytomas. The cells look very different from normal cells. They invade nearby tissues and primarily occur in the cerebrum. They are also called high-grade astrocytomas or gliomas and often recurs.
- Brain stem gliomas are located at the junction of the brain and spinal cord. They may be of any grade. Treatment depends upon cancer grade and location.
However, location may not allow for surgical removal.
- Ependymomas grow from the lining of the ventricles of the brain and the hollow central canal of the spinal cord. Most ependymomas are slow growing. There are different grades of ependymal cancers. Well-differentiated ependymomas look much like normal cells and grow slowly. Anaplastic ependymomas do not look like normal cells and grow more quickly than well-differentiated ependymal cancers. Read more about Ependymomas (PDF) in this publication by Dr. Marc Chamberlain.
(Ependymoma image courtesy of Dr. Trent Tredway.)
Oligodendrogliomas begin in brain cells called oligodendrocytes, which provide support around nerves by building a sheath of myelin and facilitating electrical nerve impulses.
Genetic testing is important for these cancers. This helps predict prognosis and treatment response. There are different grades of oligodendroglial cancers, which are defined by how the cells look under a microscope.
• Well-differentiated oligodendrogliomas (Grade II) are slow-growing cancers that look very much like normal cells.
• Anaplastic oligodendrogliomas (Grade III) grow more quickly and the cells look very different from normal cells.
Mixed gliomas start from two types of glial cells, usually astrocytes and oligodendrocytes. They account for 1 to 5 percent of all brain cancers and treatment is based on whichever cell type is the most aggressive.
Primary Cancers from Non-Glial Cells
Meningioma is cancer that arises from the meninges, the coverings of the brain and spinal cord. These are usually slow-growing cancers and can be one of three grades. Surgery is usually the treatment, however radiation therapy is often used.
Pineal Tumors are a mixture of tumors and cancers that occur near or around the pineal gland. Pineal tumors account for 1 percent of all brain cancers. The pineal gland is deep inside the brain and produces melatonin. There are several types of pineal tumors, some are cancerous. Some pineal tumors are fast growing. Surgery may be recommended for these tumors.
Pituitary Tumors affect the pituitary gland and occur in 12 to 23 percent of all people. Pituitary tumors account for about 10 percent of all brain tumors. The pituitary gland is located at the base of the brain and is responsible for hormones, growth, and metabolism. Surgery is often done for these tumors as well as radiotherapy.
Schwannomas are tumors from schwannoma cells. Schwannoma cells form the myelin sheath that covers and protects the nerves. Schwannomas are usually benign and account for 10 percent of all brain cancers. There are several types of schwannoma tumors. One more common type is an acoustic schwannoma. This is a benign tumor of the nerve for hearing. Surgery is the primary treatment. There may be multiple schwannoma tumors. In this case, surgery may be followed by radiation therapy.
Primary Central Nervous System Lymphoma is cancer that arises from lymphocytes, a kind of white blood cell. Lymphomas of the brain are a form of non-Hodgkin’s lymphoma, a cancer that occurs in the body and often in relationship to lymph nodes. These cancers are usually near the ventricles of the brain. There may be multiple tumors. Metastasis or spread of this tumor is quite common.
Secondary or Metastatic Cancers are cancers start from cancers in other organs of the body. For example, lung or breast cancer can spread to the brain. These cancers are treated with surgery, chemotherapy, and/or radiation therapy.