Although the clinical significance of proliferation activity in the subgroups of BC patients has been not well-defined [43], the results presented here show that CKAP2 expression correlated with survival (OS and RFS) especially in HER2-negative luminal patients (ER+/HER2−), but not in HER2+ patients, which is also in agreement with Sim and colleagues [42]. Here, ESR1 is linked to breast cancer.