A brain tumor is an abnormal growth of cells that develops either within the brain or in the surrounding areas. Tumors affecting the brain and spinal cord together are known as central nervous system (CNS) tumors.

Brain tumors can be benign (non-cancerous) or malignant (cancerous), and their rate of growth varies. While only about one-third of brain tumors are malignant, both benign and malignant tumors can cause serious health problems if they grow large enough to press on nearby nerves, blood vessels, or brain tissue. This pressure can interfere with normal brain function and lead to significant symptoms.