Brain tumors are abnormal masses of cells that arise in the brain.
A brain tumor may be cancerous or benign, which means noncancerous. Our brains are tightly contained within the closed cavity of our skulls. There is very little extra room within the bony skull cavity. A growing brain tumor can destroy brain cells directly or by putting pressure on the tissue surrounding the tumor. The most common cancerous brain tumors are metastatic, meaning they have spread through the bloodstream to the brain from cancer in another part of the body.