Moreover, given that there is a great demand for new biomarkers to predict outcomes and enhance individualized treatment due to breast cancer heterogeneity and that there is a lack of information about CAND1′s potential as a breast cancer prognostic biomarker, the aim of this study was to explore the significance of CAND1 in ERα-positive breast cancer by utilizing several bioinformatics tools. The gene discussed is ESR1; the disease is breast cancer.