A primary brain tumor is a mass created by the growth or uncontrolled proliferation of abnormal cells in the brain. The cause of primary brain tumors is unknown. Primary brain tumors may be located in only a small area or spread to nearby areas (invasive), non cancerous (benign) or cancerous (malignant).
Brain tumors are classified depending on the exact site of the tumor, the type of tissue involved, and whether or not it is cancerous. Brain tumors can directly destroy brain cells; or indirectly damage cells by putting pressure on other parts of the brain, leading to swelling and increased pressure within the skull.