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General Pathology

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


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


Low-grade astrocytoma

Fibrillary low-grade astrocytoma; one feature, usually atypia


Anaplastic astrocytoma

Anaplastic astrocytoma; two features


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




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