The majority of normal cells grows old and dies. New cells replace them. But sometimes an altered process occurs. The old cells or damaged cells do not die and new cells form, even though unneeded by the body. The extra cells often result in a mass of tissue or a tumor.

A brain tumor is a mass or an abnormal growth of tissue in the brain or inside the skull. Brain tumors, unlike other tumors , spread by local extension and rarely spread or metastasize outside the brain. The tumor can be benign (non-cancerous) or malignant (cancerous). A tumor which originates in the brain tissue is categorized as a primary brain tumor , while a secondary or metastatic brain tumor is cancer that has spread to the brain tissue from other parts of the body.

• Malignant tumors are more serious and often life-threatening
• Cells can break from the malignant brain tumor, spreading to other parts of the brain or to the spinal cord. Rarely do these cancerous cells spread to other parts of the body

• When removed, benign brain tumors seldom return
• Benign tumors can turn into malignant tumors

• Incidence rate of all primary non-malignant and malignant brain and central nervous system tumors: 16.5 per 100,000 persons. The rate is slightly higher among females, 17.2 versus 15.8 per 100,000 for males¹
• Incidence rate for malignant brain tumors only: 7.3 per 100,000; for non-malignant: 9.2 per 100,000¹
• 52,200 were expected to be newly diagnosed in 2008 with a primary brain tumor (malignant and benign)⁴
• 3,750 children were diagnosed with a primary brain tumor (benign or malignant) in 20071
• Survival rates are reportedly higher for children than adults (66 percent of children under 20 will be living five years after a malignant tumor diagnosis, while it is 32 percent for adult women and 29 percent for adult men)⁶
• During one's lifetime, the chance of developing a malignant or central nervous system brain tumor is less than one percent⁷
• Under age 20, 4.5 per 100,000 persons will be diagnosed with a malignant tumor1, but as a person's age increases, the risk increases. The rate at age 75 is 57 per 100,000^{1 &4}
• 12,740 deaths were attributed to primary and central nervous system tumors in 2007 in the U.S.⁵

• Headaches, which become increasingly painful
• Nausea or vomiting
• Sleepiness or lethargy
• Seizures
• Loss of balance or dizziness
• Changes in personality
• Sudden loss of vision
• Memory loss
• Speech issues
• Sensory changes
• Weakness or paralysis on one side of the body

• Grade I — tissue is benign and cells look nearly normal and grow slowly
• Grade II — tissue is malignant and cells are not normal, assuming a different look than those of a grade I tumor
• Grade III — malignant tissue has cells that are considerably different than normal cells and tend to grow rapidly
• Grade IV — malignant tissue includes cells that are most abnormal and tend to grow quickly

Low-grade tumors can become high-grade tumors. The change to a high-grade tumor occurs more often among adults than children.