MKI67 and breast cancer: Accordingly, the following subtypes of breast cancer are generally recognized: luminal A, (ER/PR+, HER2−, Ki67 low), luminal B (ER+, HER2−, Ki67 high or PR- and ER+, HER2+), HER2 overexpressed (ER/PR−, HER2+), and basal-like triple negative breast cancer (TNBC) (ER−, PR−, HER2−) (Yin et al., 2020).