Brain cancer or brain tumors are masses of abnormal cells that have grown out of control. In most other parts of the body, it is very important to distinguish between benign (non-cancerous) and malignant (cancerous) tumors.
Noncancerous tumors can usually be removed and are not likely to recur. Other tumors are malignant (cancerous). These tumors interfere with vital functions and are life threatening. Cancerous brain tumors usually grow rapidly, crowding and invading tissue. Benign tumors in other parts of the body do not invade nearby tissues or spread to distant areas, so they are almost never life threatening. One of the main reasons cancers are so dangerous is because they can spread throughout the body.
Primary brain tumors (gliomas) start in the brain and affect the central nervous system (CNS). They can be noncancerous or cancerous. Secondary brain tumors, which are 10 times more common, are cancers that originated elsewhere in the body and have metastasized (spread) to the brain. Secondary tumors are about 3 times more common than primary tumors of the brain.
Although brain tumors rarely spread to other parts of the body, most of them can spread through the brain tissue. Even so-called benign tumors can, as they grow, destroy and compress normal brain tissue, causing damage that is often disabling and sometimes fatal. For this reason, doctors usually speak of “brain tumors” rather than “brain cancers.” The main concerns with brain tumors are how readily they spread through the rest of the brain or spinal cord and whether they can be removed and not come back.