HR and breast carcinoma: Prevalence data for the overall HER2− population have not been widely reported, but the prevalences for HR+, HER2− and HR−, HER2− subgroups in the current study are considerably lower than were reported in a study using the Surveillance, Epidemiology, and End Results (SEER) database of the National Cancer Institute from 2010 to 2013, which included patients with HR+, HER2− (5.5%) and HR−, HER2− (11.4%) breast cancer [20].