Given the chromosomal location of the PPP2R1A gene (19q13.1-13.4) this scarcity is surprising, because the LOH of this locus is expected in 25% of GBM, and per definition, 100% of oligodendroglioma, IDH mutant and 1p/19q-codeleted tumors [61]. Here, IDH1 is linked to glioblastoma.