IDH1 and astrocytoma (excluding glioblastoma): Representative IHC and mutational analysis for the IDH1 gene in GII and GIV astrocytomas are shown in Figure 2A. Strong immunoreactivity for IDH1‐R132H mutant protein was mainly observed in cytoplasmic areas and was positively correlated with the gene mutations affecting codon 132 (CGT to CAT) (Table S1).