Nervous system cancer encompasses malignant tumors originating in the central nervous system (CNS), which includes the brain and spinal cord, as well as primary cancers of the peripheral nerves or spinal roots. This category includes high-grade tumors such as glioblastoma multiforme, ependymoblastoma, diffuse intrinsic brain stem gliomas, and other aggressive malignancies that may be primary, metastatic, progressive, or recurrent following initial anticancer therapy.