ESR1 and breast carcinoma: The dysregulation of hormonal signaling and other pivotal intracellular pathways is central to breast cancer pathogenesis and resistance development.[86] ER and progesterone receptors (PR) are steroid hormone receptors expressed in approximately three‐quarters of breast cancers, classifying them as hormone receptor‐positive (HR+).[87] The status of these receptors, typically determined by immunohistochemistry, dictates sensitivity to endocrine therapy.