The molecular subtypes of breast cancer range in both receptor expression and prognoses: luminal A (ER and/or PR+/HER2-), luminal B (ER and/or PR+/HER+), HER2-enriched (ER-/PR-/HER2+), and triple negative (ER-/PR-/HER2-) (2). Here, ESR1 is linked to breast carcinoma.