IDH1 and astrocytoma (excluding glioblastoma): Patients with IDH mutant tumors are generally younger with a median age at diagnosis of 37 years for patients with grade 3 astrocytoma and 47 years for grade 4 astrocytoma and grade 3 oligodendroglioma (Hartmann et al., 2009; Eckel-Passow et al., 2015).