Tumors arise in both parts of the nervous system, but nine out of 10 nervous system cancers occur in or around the brain. Glioma is a general term that includes any tumor arising from glial cells. Among adults, the most frequent types are astrocytic tumors, meningioma, acoustic neuroma, and pituitary gland tumors. In general, astrocytic tumors occurring among adults are more malignant and carry a graver prognosis than those seen among children.
Meningiomas arise from cells in the membranes that surround the brain and spinal cord.
However, even benign and slow-growing tumors of the nervous system can produce serious neurologic symptoms. The skull has no flexibility to accommodate a growing tumor mass, so as tumors grow, they exert pressure on neighboring nerve tissue. Breast cancer, for example, often metastasizes to the brain and spinal cord. Melanoma and cancers of the lung, kidney, and gastrointestinal tract also sometimes metastasize to the brain. Incidence rates for brain and other nervous system cancers vary with sex, race, and country as well as with age.