Multiple grading systems for astrocytomas exist.
The Kernohan grading system is a 4-point scale of progressive malignancy that is structured as follows:
I. Benign Astrocytoma
II. Low-Grade Astrocytoma
III. Anaplastic Astrocytoma
IV. Glioblastoma Multiforme
Grades I and II
- Well-differentiated or low-grade tumors
- Low to moderate cellularity without mitoses
- Generally follow an indolent course
Grades III and IV
- Poorly differentiated or high-grade tumors
- Highly cellular neoplasms that are mitotically active and have potential for metastases
- Clinically aggressive
Patients with grade III tumors survive longer than those with Grade IV tumors
Few patients with grade IV survive beyond 2 years and 30 - 40% of grade III patients survive 3 - 5 years
The World Health Organization grading scheme is based on the appearance of certain characteristics: nuclear atypia, mitoses, endothelial proliferation, and necrosis. These features reflect the malignant potential of the tumor in terms of invasion and growth rate.
The WHO grading scheme classifies astrocytomas as follows:
I. Juvenile Pilocytic astrocytoma
II. Low-grade astrocytoma (one feature, usually atypia)
III. Anaplastic astrocytoma (two features)
IV. Glioblastoma multiforme (tumors with 3 or 4 features and the presence of necrosis felt to be consistent with GBM)
Tumor Grade |
Kernohan Scheme |
WHO Scheme |
I |
Benign astrocytoma |
Juvenile Pilocytic astrocytoma; generally have no features, however they may have a few mitoses or endothelial proliferation without any change in prognostic significance |
II |
Low-grade astrocytoma |
Fibrillary low-grade astrocytoma; one feature, usually atypia |
III |
Anaplastic astrocytoma |
Anaplastic astrocytoma; two features |
IV |
Glioblastoma multiforme |
Glioblastoma multiforme; tumors with 3 or 4 criteria, presence of necrosis felt to be consistent with GBM.
Pallisading necrosis is also pathognomic of GBM. |
Benign or low grade astrocytomas in the Kernohan scheme correspond to grade II in the WHO scheme. Anaplastic astrocytoma and glioblastoma multiforme in the Kernohan scheme correspond to grades III and IV in the WHO scheme respectively.
Link: The Atlas of Genetics and Cytogenetics in Oncology and Hematology:
Nervous system: Astrocytic tumors
