This category encompasses anaplastic astrocytoma (AA) and glioblastoma (GBM). Although both are “malignant”, AA and GBM have distinct differences. Among 1265 patients with malignant astrocytomas, the mean age was 46 yrs for AA, and 56 yrs for GBM. Mean duration of symptoms pre-op: 5.4 mos for GBM, and 15.7 mos for AA. Malignant astrocytomas may develop from low grade astrocytomas via dedifferentiation, however they may also arise de novo.