Core needle biopsies were obtained, and the pathology of the breast mass showed Nottingham grade 3/3 invasive ductal carcinoma with significant nuclear atypia, pleomorphism, and large giant cells with anaplastic-type morphology, with estrogen receptor positive at 80% with moderate staining intensity (Figure 2), progesterone receptor negative at 0% staining intensity, ErbB2 negative at 0+, and a high Ki-67 of >90%. The gene discussed is ESR1; the disease is invasive ductal breast carcinoma.