Using tissue microarrays (TMAs) comprising two to four tumor cores for each of 1085 cases from the Carolina Breast Cancer Study (CBCS) in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium, we identified cases with core-to-core discordance in ER, PR, and HER2 status using automated digital image analysis. The gene discussed is ESR1; the disease is breast carcinoma.