Surov A, et al. - In this multicenter analysis, researchers investigated the associations between apparent diffusion coefficient (ADC) and expression of Ki-67 and tumor grade in breast cancer (BC). Study participants were 870 patients (all female; mean age, 52.6 ± 10.8 years), with breast magnetic resonance imaging with diffusion-weighted imaging. Findings revealed that ADC values failed to differentiate high/moderate grade tumors from grade 1 lesions, as seen in ROC analysis. Furthermore, ADC showed a weak statistically significant correlation with expression of Ki-67. Overall, based on the findings, ADC cannot serve as a surrogate marker for proliferation activity and/or for tumor grade in breast cancer.