MKI67 and breast cancer: In this study, we aimed to investigate the frequency and causes of receptor discordances in breast cancer encountered after currently used NACTx regimens, their clinical significance in terms of adjuvant therapy requirements, the effect of NACTx on hormone expression levels, the Ki-67 proliferation index, and the tumor grade and to search for parameters that may indicate chemosensitivity by analyzing features of chemo-sensitive and chemo-resistant tumors.