MRI features of molecular glioblastoma: morphological and advanced imaging insights

IDH-wildtype diffuse gliomas with molecular features of glioblastoma (mGBM) were integrated into the GBM category in the 2021 WHO classification, yet their MRI characteristics remain poorly described. This study aimed to detail morphological and advanced MRI features of mGBM to improve diagnostic accuracy and management.

MRI scans (1.5 T or 3 T) of 72 patients with histomolecularly confirmed mGBM were retrospectively reviewed. Two neuroradiologists analyzed morphological features (necrosis, contrast enhancement, FLAIR pattern, multilobar involvement) and advanced imaging findings (diffusion, perfusion).

Mean patient age was 63 years. mGBMs showed a broad spectrum of MRI appearances, from grade 2-like (39%) to grade 4-like (26%). Infiltrative FLAIR hyperintensity was nearly constant, frequently with multilobar involvement (65%). Contrast enhancement was absent in 39% or faint/limited when present, often mimicking lower-grade gliomas. Gyriform cortical infiltration sparing white matter was seen in 15% of cases, less than previously reported. Advanced imaging showed diffusion restriction in 64% and elevated rCBV (>1.75) in 88% of cases with perfusion data, leading to reclassification of 22% of morphologically grade 2-like lesions as grade 3-like.

mGBMs often mimic low-grade gliomas, exposing patients to underdiagnosis and treatment delays. However, infiltrative FLAIR abnormalities, multilobar involvement, diffusion restriction, or increased perfusion should raise suspicion, particularly in older patients. This cohort describing both morphological and advanced MRI features of mGBM provides practical imaging criteria to enhance early recognition in routine practice.