TP53 and astrocytoma (excluding glioblastoma): The third subgroup, called the H3-K27M subgroup of DIPGs, was highly mutated either at the level of histone H3.3 or H3.1 and is characterized by highly unstable genomes; TP53 mutations are frequent in these tumors, as well as PDGFRA amplifications; approximately 20% of these patients display ACVR1 mutations; at the histological level, the large majority of these tumors were high-grade astrocytomas [61].