In a 2012 study of pediatric GBM, somatic mutations in the H3.3-ATRX-DAXX chromatin remodeling pathway were found in 44% (21/44) of tumors; however, under the new WHO CNS 5 criteria, two of the tumors included in this analysis would not be classified as glioblastoma due to IDH mutations [5,33]. This evidence concerns the gene IDH1 and glioblastoma.