ESR1 and triple-negative breast carcinoma: Joint evaluation of the immunohistochemical staining (IHC) statuses of ER, PR, and HER2 can further divide patients into subtypes, such as hormone-receptor-positive breast cancer (ER+/PR+)3 or triple-negative breast cancer (ER−/PR−/HER−)4–6, which are relevant for prognosis.