A brain tumor develops from an abnormal growth of cells in the brain. There are more than 120 types of brain tumors, classified by:
- The location of the cancerous cells
- How the cancerous cells behave
- The rate of cancerous cell growth.
Primary Brain Tumors
Primary tumors are also called “true brain tumors.” Primary brain tumors originate in the brain and tend to stay in the brain, rather than spread elsewhere. A primary brain tumor is named for the part of the brain or the type of cells from which it originates. Examples of primary brain tumors include:
- Medulloblastomas: Develop in the cerebellum
- Pineal region tumors: Arise in or near the pineal gland
- Schwannomas: Originate in Schwann cells that line a peripheral nerve, for example, in the inner ear.
Doctors don’t know what causes primary brain tumors, but certain factors put people at increased risk for developing a primary brain tumor. Some risk factors for developing a primary brain tumor include:
- Age (those under eight or over 70 are at increased risk)
- Family history of gliomas
- Gender (males are more likely to develop primary brain tumors)
- Race (Caucasians are at increased risk).
People who work with radiation or certain chemicals, such as formaldehyde or vinyl chloride, also have a higher incidence of primary brain tumors.
Secondary Brain Tumors
Secondary brain tumors are far more common than primary tumors. Also called “metastatic tumors,” secondary brain tumors originate in other organs or tissues and migrate into the brain. A secondary brain tumor may be diagnosed in someone with a prior history of cancer somewhere else in the body, or it may be the first symptom of cancer that began elsewhere and spread to the brain. Any type of cancer can spread to the brain, but common migrating cancers are:
- Breast cancer
- Colon cancer
- Kidney cancer
- Lung cancer
Benign Brain Tumors
Benign brain tumor cells are noncancerous and don’t spread to other parts of the body or invade any surrounding tissues. The edges of these tumors are much more distinct than cancerous tumors, making it easier for a surgeon to excise them from brain tissue. Benign tumors very rarely become malignant, and rarely reappear once removed. Although not cancerous, a benign brain tumor can still be dangerous. As it increases in size, it exerts more pressure on potentially sensitive areas of the brain. Depending on the size and location of the tumor, this increase in pressure can make symptoms much worse.
Malignant Brain Tumors
Malignant brain tumors are cancerous and often life-threatening, and the cells forming the mass can continue reproducing unchecked and may invade healthy brain tissue. These tumors can grow quickly and interfere with normal brain function as they grow larger and larger. Metastasis can occur when a piece of the cancerous mass breaks off and migrates away from the brain, but this type of spreading is uncommon.
Mayo Foundation for Medical Education and Research Staff. (2008). Brain tumor. Retrieved on March 20, 2010, from the Mayo Clinic website: http://www.mayoclinic.com/health/brain-tumor/DS00281.
MedicineNet Staff. (n.d.). Brain tumor. Retrieved on March 20, 2010, from the MedicineNet.com website: http://www.medicinenet.com/brain_tumor/article.htm.