Specifically, this set of genes (CD81, HCK, HOXA5, ASCL2, TES, AHR, DIO3, FZD9 and MOS) exhibited large DNA methylation increments when comparing grade II PXAs and grade II PXA-4 case precursor of the anaplastic PXA-5; were consistently methylated in anaplastic PXA and in GBM patients as well (β > 0.4) but unmethylated (β < 0.2) in normal brain, thus indicating an association between increasing rate of hypermethylation events and the presence of histological malignant features. This evidence concerns the gene MOS and pleomorphic xanthoastrocytoma.