Table 2 The definition of astrocytoma, IDH-mutant.

From: Grading of adult diffuse gliomas according to the 2021 WHO Classification of Tumors of the Central Nervous System

• Astrocytoma, IDH-mutant, grade 2

 A diffusely infiltrative astrocytic glioma that is well differentiated and lacks histologic features of anaplasia. Mitotic activity is not detected or low. Microvascular proliferation, necrosis, and CDKN2A/B homozygous deletions are absent

• Astrocytoma, IDH-mutant, grade 3

 A diffusely infiltrative astrocytic glioma that exhibits focal or dispersed anaplasia and displays significant mitotic activity. Microvascular proliferation, necrosis and CDKN2A/B homozygous deletions are absent

• Astrocytoma, IDH-mutant, grade 4

 A diffusely infiltrative astrocytic glioma that exhibits microvascular proliferation or necrosis or CDKN2A/B homozygous deletion or any combination of these features

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