T2-FLAIR mismatch sign, which is defined as the presence of complete/near-complete hyperintense signals on a T2-weighted image and a relatively hypointense signal on FLAIR except for a hyperintense peripheral rim, has been suggested7 and validated as a highly specific imaging marker of IDH-mutant astrocytomas, with specificity as high as 100%8. This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).