MRI features and imaging-pathology correlation of oligodendroglioma with IDH mutation and 1p/19q codeletion.

OBJECTIVE: To characterize routine magnetic resonance imaging (MRI) manifestations of molecularly defined isocitrate dehydrogenase (IDH)-mutant, 1p/19q codeleted oligodendroglioma, to introduce two newly proposed intratumoral imaging signs, assess their diagnostic efficacy, and interpret their histologic basis via voxel-wise imaging-pathology matching. MATERIALS AND METHODS: 36 surgically validated oligodendrogliomas were retrospectively analyzed per the 2021 WHO CNS tumor criteria; MRI signals were correlated with histologic indices such as cellular density and myxoid microcystic change. RESULTS: The cohort comprised 24 males and 12 females with a mean age of (30.9 ± 16.1) years. All supratentorial lesions were mostly cystic-solid, showing T1-hypointense solid parts, T2/fluid-attenuated inversion recovery (FLAIR) slightly hyperintense parenchyma, T2-hyperintense cysts, and heterogeneous enhancement, predominantly WHO grade 2. No intergrade differences in baseline MRI/clinical features were found (p > 0.05). Cross-sectional prevalence: isolated ripple sign 16.7%, isolated finger-like cystic sign 8.3%, dual signs 5.6%, total positivity 30.6%. Separate κ values (0.81 and 0.83) revealed excellent inter-rater consistency; the two signs occurred independently (p > 0.05) with high specificity but low sensitivity. Histologically, the ripple sign stemmed from alternating hypercellular and microcystic grey-white matter bands, whereas finger-like cysts arose from tract-aligned fused microcysts. CONCLUSION: This glioma entity mostly presents as infiltrative supratentorial cystic-solid masses. The two novel signs serve as high-specificity auxiliary markers but lack sufficient sensitivity; large multi-center validation is warranted. Integrated MRI and pathological correlation elevate preoperative diagnostic accuracy.