The diffuse midline glioma, H3 K27M-mutant, shows a lysine to methionine substitution at position 27 of the H3 histone family member 3A (H3F3A) or histone cluster 1 H3 family member 3B (HIST1H3B) gene and is included in the WHO 2016 classification as a separate entity. Here, H3-3A is linked to diffuse midline glioma.