MKI67 and breast cancer: We therefore analyzed the performance of Ki67 staining in pre- versus postmenopausal breast cancer patients treated with tamoxifen, enrolled in a neo-adjuvant, endocrine therapy study by comparing the change in IHC-based Ki67 assessed by pathologists and artificial intelligence to gene expression-based Ki67, gene expression signatures capturing proliferation, mitotic figure counts as well as blood levels of tamoxifen or its metabolites and estradiol.