In ascending order of malignancy, astrocytomas are classified as Grade I: Pilocytic astrocytomas and subependymal giant cell astrocytomas (most common in tuberous sclerosis) Grade II: Low-grade astrocytomas, including pleomorphic xanthoastrocytoma Grade III: Anaplastic astrocytomas Grade IV: Glioblastomas and diffuse midline gliomas Pilocytic, other low-grade, or anaplastic astrocytomas tend to develop in younger patients.