IDH1 and Meckel syndrome, type 1: Both clinical and preclinical studies demonstrated that patients with PN GBM subtype respond better to radio and chemotherapy, with a better prognosis compared to patients with the MES subtype.[14, 16, 35] IDH mutations are common in the PN subtype, thus responsible for the favorable outcome in this subtype.[23] Brennan and others[128, 129] demonstrated that PN GBMs manifest the cytosine‐phosphate‐guanine island methylator phenotype (G‐CIMP) and tumors with both IDH1 mutation and G‐CIMP have better prognosis, while G‐CIMP negative and wt IDH1 GBM show similar prognosis to the MES subtype.