Central nervous system (CNS) tumors are a type of cancer that starts in the cells of the brain or spinal cord. These tumors can be either benign (noncancerous) or malignant (cancerous). CNS tumors can occur in both adults and children, and can affect any part of the brain or spinal cord. Treatment for CNS tumors depends on the type and location of the tumor, as well as the patient's age and overall health.