IDH1 and diffuse midline glioma: The four pediatric types of DHGGs (all grade 4 tumors) are represented by the (1) diffuse midline glioma, H3 K27-altered; (2) diffuse hemispheric glioma, H3 G34-mutant; (3) diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype; and (4) infant-type hemispheric glioma (1).