Likewise, the traditional pooling of “high-grade astrocytomas” (grades 3 and 4) should be discouraged as IDH-mutant grade 3 astrocytoma differs in molecular profile and clinical behaviour compared with IDH-wildtype grade 4 astrocytoma (i.e. glioblastoma). This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).