We characterized these three classes of patients to see if some are associated with higher residual cancer burden (RCB), which is clinically similar to pCR/RD classification; whether they correspond to some of the breast cancer subtypes defined by the PAM50 molecular classifier; and whether they differ in Ki-67 or androgen receptor (AR) expression, which are known to impact the aggressiveness of breast cancers. This evidence concerns the gene MKI67 and breast cancer.