This updated classification system categorizes diffuse gliomas into three distinct types: oligodendroglioma with IDH1/2 mutation and 1p/19q co-deletion, astrocytomas with IDH1/2 mutations but without co-deletion, along with TP53 mutations and ATRX loss; and GBM with wild-type IDH1/2. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).