In 2010, the American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) published the guideline for ER/PR immunohistochemical (IHC) detection, which clearly proposed that the expression level of ER/PR should be detected in all newly diagnosed breast cancer patients, and emphasized the basic operating procedures, quality control and result interpretation criteria of ER/PR detection (23). The gene discussed is ESR1; the disease is breast cancer.