Advanced MRI Findings in Medulloblastomas: Relationship to Genetic Subtypes, Histopathology, and Immunohistochemistry

BACKGROUND AND PURPOSE For diagnosis of medulloblastoma, the updated World Health Organization classification now demands for genetic typing, defining more precisely tumor biology, therapy, and prognosis. We investigated potential associations between magnetic resonance imaging (MRI) parameters including apparent diffusion coefficient (ADC) neuropathologic features focusing on subtypes. METHODS This study was a retrospective single-center analysis 32 patients (eight females, median age = 9 years [range, 1-57], mean 12.6 ± 11.3) from 2012 to 2019. Genetic subtypes (wingless [WNT]; sonic hedgehog [SHH]; non-WNT/non-SHH), histopathology, immunohistochemistry (p53, Ki67), following MRI were correlated: volume, location (midline, pontocerebellar, cerebellar hemisphere), edema, hydrocephalus, metastatic disease (presence/absence each), contrast-enhancement (minor, moderate, distinct), cysts (none, small, large), hemorrhage minor, major), ADCmean. The ADCmean calculated using manually set regions interest within solid tumor. Statistics comprised univariate multivariate testing. RESULTS Out tumors, three tumors WNT activated (9.4%), 13 (40.6%) SHH activated, 16 (50.0%) non-WNT/non-SHH. Hemispherical (n 7/8, P .003) presence edema (8/8; < .001, specificity 100%, positive predictive value 100%) significantly associated with activation. combined parameter “no + no cysts” discriminated WNT-activated SHH-activated medulloblastoma (P .036). (10–6 mm2/s) 484 WNT-activated, 566 SHH-activated, 624 non-WNT/non-SHH .080). A significant negative correlation found Ki67 (r –.364, .040). CONCLUSION enabled noninvasive differentiation medulloblastoma. ADC alone not reliable characterization, but proliferation rate.