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Updated: Mar 29, 2026
A Protocol for Explant Cultures of IDH1-mutant Diffuse Low-grade Gliomas
Published on: May 9, 2025
Conventional MRI/CT for differentiation of IDH-mutant adult-type diffuse gliomas: revisited with a new imaging
Yuji Ohizumi1, Ryo Kurokawa2, Yusuke Watanabe1
1Department of Radiology, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Purpose:
To test whether a refined definition of the T2-FLAIR mismatch sign (redefined T2FM) and a newly defined subcortical FLAIR signal drop (scFLAIR-D) on conventional MRI improve presurgical discrimination between astrocytoma, IDH-mutant (AST) and oligodendroglioma, IDH-mutant and 1p/19q-codeleted (ODG).
Materials And Methods:
In this single-center retrospective study (January 2021-July 2025), adults with IDH-mutant adult-type diffuse glioma and preoperative T2-weighted and FLAIR MRI were included. Two blinded readers (with senior adjudication) scored five features: redefined T2FM (includes partial but excludes subcortical-only mismatch), scFLAIR-D (focal FLAIR hypointensity confined to subcortical white matter within T2-hyperintensity), multiple necrotic/cystic foci (≥ 2 cavities), cortical predominance (> 50% cortical volume), and calcification (CT).
Results:
Forty-one patients were included (median age 42 years; 24 men; 16 AST, 25 ODG). AST significantly more often showed redefined T2FM (AST: 87.5% [14/16] vs. ODG: 20.0% [5/25]; p < 0.001) than ODG. ODG significantly more often showed scFLAIR-D (AST: 6.3% [1/16] vs. ODG: 44.0% [11/25]; p = 0.013), multiple necrotic/cystic foci (12.5% [2/16] vs. 56.0% [14/25]; p = 0.008), and calcification (0% [0/16] vs. 50.0% [12/24 patients with preoperative CT]; p < 0.001); cortical predominance trended higher (31.3% [5/16] vs. 64.0% [16/25]; p = 0.058). For predicting AST, redefined T2FM achieved 87.5% sensitivity and 80.0% specificity. For predicting ODG, scFLAIR-D achieved 44.0% sensitivity and 93.8% specificity. Two or more ODG-favored features (scFLAIR-D, multiple necrotic/cystic foci, calcification) identified ODG with 100% specificity, whereas redefined T2FM without ODG-favored features identified AST with 96.0% specificity.
Conclusion:
A refined T2FM definition improves sensitivity for AST while preserving high specificity. scFLAIR-D serves as a simple, specific marker of ODG; in combination, these routine features yield high rule-in specificity to support presurgical planning and early therapeutic counseling. Refining T2FM to include partial but exclude subcortical-only mismatch increased sensitivity for astrocytoma, IDH-mutant (87.5%) while preserving specificity (80.0%). Newly defined scFLAIR-D was highly specific for oligodendroglioma, IDH-mutant and 1p/19q-codeleted (93.8%). Combining these qualitative MRI/CT features yielded high rule-in specificities for lineage discrimination.
