A brain tumor is a disease in which abnormal cells form in the tissues of the brain.
There are many types of brain and spinal cord tumors. The tumors are formed by the abnormal growth of cells and may begin in different parts of the brain or spinal cord. Together, the brain and spinal cord make up the central nervous system (CNS).
The tumors may be benign (not cancer) or malignant (cancer). Benign brain tumors grow and press on nearby areas of the brain. They rarely spread into other tissues and may recur (come back). Malignant brain tumors are likely to grow quickly and spread into other brain tissue. When a tumor grows into or presses on an area of the brain, it may stop that part of the brain from working the way it should. Both benign and malignant brain tumors can cause symptoms and need treatment.
Brain tumors can occur in both adults and children. However, treatment for children may be different than treatment for adults.
Source: U.S. Department of Health & Human Services-NIH