IDH1 and diffuse astrocytoma: Moreover, “Astrocytoma, IDH-mutant” is a diffuse astrocytoma with activating mutation in IDH1 or IDH2 (as well as altered ATRX, TP53, or CDKN2A expression) that is graded 2-4 within type, abolishing the term “GBM, IDH-mutant”.