MedGen

Glioblastomas are malignant astrocytic tumors (grade IV according to the WHO classification). [from ORDO]

A tumor arising from glia in the central nervous system with macroscopic regions of necrosis and hemorrhage. Microscopically, glioblastoma multiforme is characterized by regions of pseudopalisading necrosis, pleomorphic nuclei and cells, and microvascular proliferation. [from HPO]

Oligoastrocytoma is a type of low-grade glioma with a mixed astrocytoma and oligodendroglioma histology, manifesting with headaches, speech and motor problems, seizures and, in some, subarachnoid haemorrhage. [from ORDO]

A rare variant of diffuse astrocytoma. It is predominantly composed of neoplastic astrocytes showing a small cell body with few, flaccid processes with a low content of glial filaments and scant GFAP expression. This lesion is not well defined and is considered by some authors as an occasional histopathological feature rather than a reproducibly identifiable variant. When occurring in children, this neoplasm may be difficult to separate from pilocytic juvenile astrocytoma. (Adapted from WHO) [from NCI]

Astrocytoma is a neoplasm of the central nervous system derived from astrocytes. Astrocytes are a type of glial cell, and thus astrocytoma is a subtype of glioma. [from HPO]