IDH1 and central nervous system cancer: Previous studies have observed that some genetic variants are associated with tumor grade, like risk variants in the CDKN2B, RTEL1, and TERT regions [18, 31], which show association with high grade glioma, while risk variants in the CCDC26 and PHLDB1 regions are associated with low grade glioma involving IDH mutation, and 1p/19q codeletion [17, 31].