A small number (n = 3) of tumors classified as high-grade glioma (HGG, K27wt) with germline alterations in DNA mismatch repair genes22–25 (MSH6, PMS2) showed a hypermutator phenotype2, with a median of 79.23 total mutations per megabase (Fig. 1b). Here, PMS2 is linked to glioma.