IDH1 and glioblastoma: We observed that misclassified histological WHO grade 4 IDH-wildtype glioblastomas tended to have better outcomes than correctly classified WHO grade 4 IDH-wildtype glioblastomas in our TCGA validation set and the dataset published by Jonsson et al. Given that these tumors were all histological WHO grade 4, the existence of pediatric-type diffuse glioma does not explain their relatively favorable clinical course.