IDH1 and diffuse astrocytoma: Based on the recent classification of central nervous system tumors, diffuse gliomas are categorized into four grades (I–IV) according to World Health Organization (WHO): diffuse astrocytoma (IDH mutant, WHO grade II), oligodendroglioma (IDH mutant, WHO grade II), oligoastrocytoma (IDH mutant, WHO grade II), anaplastic astrocytoma, anaplastic oligodendroglioma (IDH mutant, WHO grade II), oligoastrocytoma (IDH mutant, WHO grade III), and glioblastoma multiforme (GBM or IDH mutant WHO grade IV) [4–6].