TP53 and neoplasm: The most common genomic alterations co-occurring with H3 K27M and H3 G34V/R were in common tumor suppressors genes: TP53, ATRX, and NF1. In H3G34-mutant DHG tumors, we found TP53 and ATRX mutations in more than 90% of cases, consistent with other reports in the literature [14, 29, 32].