Somatic missense mutations in genes encoding Histone H3 isoforms, including H3F3A, HIST1H3B and HIST1H3C, were subsequently identified in up to 50% of supratentorial hemispheric pHGG, and 80% of pediatric diffuse midline gliomas (DMG), a form of pHGG in the thalamus or brainstem [11, 15, 20]. This evidence concerns the gene H3C3 and diffuse midline glioma.