Imaging features of IDH-mutant astrocytoma, grade 2

38-year-old with an IDH-mutant astrocytoma, grade 2. On FLAIR MRI (A), a large right frontal mass has relatively hypointense signal except for a peripheral rim of hyperintense signal and vasogenic edema. On T2-weighted MRI (B), the mass has nearly-uniform hyperintense signal. The difference in the signal intensity of the center of a mass on T2-weighted and FLAIR MRI is termed the "T2-FLAIR mismatch" sign and has been attributed to the presence of multiple intratumoral microcysts.