MKI67 and breast cancer: <h4>Objective</h4>This retrospective study was to develop and validate a deep learning model based on multi-phase Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) for non-invasive and accurate prediction of Ki-67 expression, a key proliferation biomarker critical for treatment decision-making and prognostic evaluation in breast cancer.<h4>Methods</h4>404 breast cancer patients who underwent preoperative DCE-MRI within 1 week of surgery were enrolled and randomly split into training (n = 282) and test (n = 122) sets in a 7:3 ratio.