IDH1 and astrocytoma (excluding glioblastoma): Grade 4 astrocytomas with IDH mutation (previously termed ‘Glioblastoma, IDH-mutant’) tend to occur in younger patients with a mean age of 32 years at diagnosis and confer a median overall survival of 31 months compared to a mean age of diagnosis at 59 years and median overall survival of 15 months for IDH-wildtype glioblastoma [10, 11, 15, 22, 26, 31, 36, 37, 39, 45, 48].