A brain tumor is a mass or growth of abnormal cells in the brain. Tumors in the brain typically are categorized as primary or secondary. Primary brain tumors originate in the brain and can be noncancerous (benign) or cancerous (malignant). Secondary brain tumors result from cancer that has started elsewhere and spread (metastasized) to the brain. Primary brain tumors are less common than secondary brain tumors are.

Benign brain tumors are usually slower growing, easier to remove (depending on their location), and less likely to recur than are malignant brain tumors. Benign brain tumors usually don't invade the surrounding normal brain or other nearby structures. Malignant brain tumors can grow rapidly, crowding or destroying nearby brain tissue. However, in a small number of cases even benign brain tumors can cause serious problems or can be life-threatening.

Brain tumors are often challenging to treat. They're the second-leading cause of cancer death in children under age 20. But the outlook isn't necessarily bleak. Many types of brain tumors can be successfully treated with one or more treatment methods. In addition, technology is enabling doctors to target tumors more precisely. And innovative treatments under investigation mean more hope for the future.

The signs and symptoms of a brain tumor depend on its size, location and rate of growth. A brain tumor — primary or secondary — can cause a variety of symptoms because it can directly press on or invade brain tissue, damaging or destroying areas responsible for sight, movement, balance, speech, hearing, memory or behavior. Pressure from a brain tumor can also cause surrounding brain tissue to swell (edema), further increasing pressure and symptoms.

Signs and symptoms can include the following:

• New and aggressive headache — especially upon awakening
• Unexplained nausea or vomiting
• Vision problems such as blurred vision, double vision or loss of peripheral vision
• Gradual loss of sensation or movement in an arm or a leg
• Difficulty with balance
• Speech difficulties
• Confusion in everyday matters
• Personality or behavior changes
• Seizures, especially in someone who doesn't have a history of seizures (as with epilepsy, for example)
• Hearing problems
• Hormonal (endocrine) disorders

Because doctors don't know exactly what causes primary brain tumors, it's difficult to pinpoint risk factors. Brain tumors sometimes strike several members of a family, suggesting heredity may be a risk factor. Heredity appears to account for a small minority of brain tumors. Overall, males and whites are more likely to develop a brain tumor.

Some types of brain tumors appear to occur more frequently in people who are exposed to radiation or certain chemicals, such as those who work in oil refining, rubber manufacturing, and chemical and nuclear industries. But a definite link between exposure to chemicals and brain tumors hasn't been proved. Similarly, electromagnetic fields and the use of cell phones have been studied as causes of primary brain tumors, but no definitive medical evidence indicates that either causes brain tumors.

Although brain tumors can occur at any age, they're most common in people older than 65. Children younger than 8 appear to be at a higher risk for brain tumors than are older children.

Doctors and researchers don't believe that head injuries increase the risk of developing a brain tumor.