PIGR and breast cancer: Furthermore, a prognostic risk model for evaluating BC patients’ OS was established based on the expression levels of the 7 vital genes stated above and their regression coefficients as described below: Risk score = (0.153 × expression level of EPCAM) + (− 0.042 × expression level of PIGR) + (− 0.040 × expression level of KRT14) + (− 0.069 × expression level of DOK7) + (0.154 × expression level of CD24) + (0.105 × expression level of CYP19A1) + (− 0.106 × expression level of CXCL13).