IDH1 and astrocytoma (excluding glioblastoma): More specifically, the highest number of patients with IDH1 mutation in tissue was found in the astrocytoma grade (G) III (38.1%), following by astrocytoma G II (23.8%), oligodendroglioma (14.3%), astrocytoma G IV (9.5%), and oligoastrocytoma (9.5%) (Table 2).