IDH2 and glioblastoma: A tripartite genetic signature was described in 2012 [6] with I-X tumors being described as similar to GBM with poor patient survival, advanced age and lacking in isocitrate dehydrogenase (IDH) and Alpha Thalassemia/Mental Retardation Syndrome X-linked (ATRX) mutations and therefore being distinct from IDH1/ATRX/TP53 (I-A) and IDH1/homolog of Drosophila capicua (CIC)/far-upstream binding protein 1 (FUBP1) (I-CF) tumors.