Table 6.

Suggested definitions and grading of Astrocytomas, IDH‐mutant.

Astrocytoma, IDH‐mutant, WHO grade 2

A diffusely infiltrative astrocytic glioma with an IDH1 or IDH2 mutation 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, WHO grade 3

A diffusely infiltrative astrocytic glioma with an IDH1 or IDH2 mutation that exhibits focal or dispersed anaplasia and displays significant mitotic activity. Microvascular proliferation, necrosis and CDKN2A/B homozygous deletions are absent

Astrocytoma, IDH‐mutant, WHO grade 4

A diffusely infiltrative astrocytic glioma with an IDH1 or IDH2 mutation that exhibits microvascular proliferation or necrosis or CDKN2A/B homozygous deletion or any combination of these features