CCNA2 and breast cancer: In addition, the expression levels of CDK1 and CCNA2 have been previously revealed to be considerably higher in breast cancer tissues than those in normal tissues, and these genes lead to breast cancer development and are related to poor prognosis (Xing et al., 2021); however, compared with their study, we found that CDK1 had an independent association with prognosis, and the discrepancy may be due to different analysis methods, as we analyzed according to the subtype while they did not.