IDH1 and oligodendroglioma: Diagnoses were grade 2 oligodendroglioma (n = 10: IDH1-mutant, yes n = 7, no n = 2, unknown n = 1; 1p/19q codeletion, yes n = 9, not known n = 1), grade 3 oligodendroglioma (n = 9: IDH1-mutant, yes n = 6, no n = 1, unknown n = 2; 1p/19q codeletion, yes n = 7, not known n = 2), and grade 2 astrocytoma (n = 9: IDH1-mutant, yes n = 6, no n = 1, unknown n = 2; 1p/19q codeletion, no n = 7, not known n = 2).