In low-grade astrocytomas, defined as IDH-mutated, non-1p/19q codeleted tumors, the T2-FLAIR mismatch sign, referring to a T2-hyperintense lesion that is hypointense on FLAIR with the exception of a hyperintense peripheral rim (131, 171, 173, 174), is quite characteristic and has an estimated sensitivity of 32% and specificity of 100% (175). This evidence concerns the gene IDH1 and astrocytoma (excluding glioblastoma).