Brain cancer can arise from many different types of brain cells (primary brain cancer) or occur when cancer cells from another part of the body spread (metastasize) to the brain. True brain cancers are those that arise in the brain itself. Grades of brain cancers indicate how aggressive the cancer is. Type of brain cancer indicates what kind of brain cells that gave rise to the tumor. Staging of brain cancers indicates the extent of spread of the cancer. Causes of brain cancer are difficult to prove; avoiding compounds linked to cancer production is advised.