ESR1 and breast cancer: Based on theexpression of these markers, BC is categorized into four primary subtypes,each with distinct prognoses and outcomes: luminal A (ER+, PR+, HER2–,low Ki-67), luminal B (ER+, PR±,HER2±, high Ki-67), HER2 overexpression(ER–, PR–, HER2+), and triple-negative (TNBC/ER–,PR–, HER2−).2 Around 40–50%of BCs are of the Luminal A subtype, while Luminal B, HER2 overexpression,and triple-negative frequencies are approximately 20–30, 15–20,and 10–20%, respectively.3 In theLuminal A subtype of BC; patients generally experience a favorableprognosis, with higher chances of overall survival.