Diffuse astrocytoma grading

Last revised by Dr Derek Smith on 14 Apr 2022

Grading of diffuse astrocytic tumors in adults has been done according to a number of systems over the years, although by far the most popular now being the WHO grading system.

Historically these grading systems focused on the presence or absence of a number of histological features, although more recently genetic/molecular markers have been introduced into the grading schema 3,6:

Histological features historically used include:

  • cellular atypia/anaplasia 
  • mitotic activity
  • microvascular proliferation
  • necrosis typically with perinecrotic palisading

Classification systems include:

Direct equivalence between the grades of various grading systems is of course not possible (otherwise they wouldn't be different systems), and thus care should be taken to state which system is being used and, in some situations, which edition; for example, the 5th edition (2021) WHO classification of CNS tumors suggests prefacing the grade by "WHO CNS" 4,6

It should be noted that it is well recognized that pathological classification has a high interobserver variation and thus imperfectly predicts clinical outcomes 5

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Cases and figures

  • Grade II
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  • Grade III
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  • Grade IV
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  • Case 4: grade 2 (diffuse astrocytoma IDH-mutant WHO CNS grade 2)
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  • Case 4: transformation to grade 4 (diffuse astrocytoma IDH-mutant WHO CNS grade 4)
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