The brain and spinal cord together make up the central nervous system (CNS). Cancer can begin in the CNS or, more commonly, it can spread there. Primary brain tumors are tumors that form from cells within the brain. Not all primary brain tumors are the same. Primary brain tumors can be divided into malignant or benign tumors:
When cancer develops elsewhere in the body and spreads (metastasizes) to the brain, it’s called a secondary brain tumor, or brain metastasis. These tumors—cancerous tumors that developed elsewhere in the body and spread to the brain—are more common than primary brain tumors, which begin in the brain cells. Cancer of the lung, colon, kidney and breast commonly metastasize to the brain.
Primary brain tumors are classified by the type of cell or tissue the tumor affects as well as the location and grade of the tumor. Brain cancer cells may travel short distances within the brain but generally do not spread beyond the brain.
The chance of developing a malignant (cancerous) brain or spinal cord tumor is less than 1 percent. Men are at a slightly increased risk—about one in 143—while women have a one in 185 chance of getting this cancer type, although women are at a greater risk for certain types of brain tumors.
Next topic: What are the risk factors for brain cancer?