In this study, we evaluated breast biomarkers ER, PR, HER2 and Ki67, together with TP53, CDKN2A (P16INK4a), cyclin-dependent kinase (CDK) inhibitor CDKN1A (P21/WAF1) in individual cancer cells of a breast tissue microarray (TMA) comprising invasive tumors. The gene discussed is ESR1; the disease is cancer.