IDH1 and astrocytoma (excluding glioblastoma): In addition to the histological subtypes of the previous classification (astrocytoma, oligodendroglioma, and oligoastrocytoma), the new criteria involve the evaluation of mutations, such as those found in the gene encoding the isocitrate dehydrogenase 1 (IDH1), the 1p/19q co-deletion, and some histone mutations.