Evaluating the super T2-FLAIR mismatch sign in non-contrast-enhancing oligodendroglioma, IDH-mutant, and 1p/19q codeleted.

The super T2-weighted imaging-fluid-attenuated inversion recovery (T2-FLAIR) mismatch sign has been identified as a prognostic imaging biomarker for non-contrast-enhancing astrocytoma, isocitrate dehydrogenase (IDH)-mutant, central nervous system World Health Organization grade 2 or 3. However, its relevance to other gliomas remains uncertain. Here, we evaluated the significance of the super T2-FLAIR mismatch sign in non-contrast-enhancing oligodendroglioma, IDH-mutant, and 1p/19q codeleted. We retrospectively analyzed oligodendroglioma cases from our institution and The Cancer Genome Atlas (TCGA)/The Cancer Imaging Archive lower-grade glioma (LGG) dataset. The super T2-FLAIR mismatch sign was defined as a markedly low signal, comparable to cerebrospinal fluid, in noncystic lesions, distinct from the conventional T2-FLAIR mismatch sign. We assessed its association with prognosis and diagnostic utility by including 33 non-contrast-enhancing astrocytoma cases from our institution and 30 from TCGA-LGG, calculating the positive predictive value (PPV) and negative predictive value (NPV). Among 19 non-contrast-enhancing oligodendroglioma cases in our dataset and 16 in TCGA-LGG, the T2-FLAIR mismatch sign was present in 1 and 3 cases, respectively, while the super T2-FLAIR mismatch sign was observed in 3 and 2 cases. The mean follow-up period was 38.8 months (our dataset) and 28.2 months (TCGA-LGG). The super T2-FLAIR mismatch sign was not associated with either progression-free or overall survival in oligodendroglioma. In TCGA-LGG, it had a PPV of 86.7% and an NPV of 45.2% (P = 0.0487) for astrocytoma. The super T2-FLAIR mismatch sign was primarily observed in astrocytoma but also appeared in non-contrast-enhancing oligodendroglioma. It served as a prognostic biomarker for astrocytoma but not for oligodendroglioma.