We analyzed the serum concentrations of biomarkers involved in carcinogenesis, which can also be targeted by therapy.<h4>Methods</h4>In a single-center prospective study, the serum levels of Aurora A, thymidine kinase 1, and human epidermal growth factor receptor type 3 (HER3) were determined in 119 women with BC before neoadjuvant treatment using ELISA kits.<h4>Results</h4>The following clinical data were analyzed: age; TNM; the expression of ER, PGR, HER2, and Ki67; histological grade (G); and the response to neoadjuvant treatment (NAT) in the residual tumor burden classification (RCB). This evidence concerns the gene MKI67 and breast cancer.