ESR1 and invasive ductal breast carcinoma: As shown in Tables S2–S4, compared with cases with grade I/II ER+HER2− tumors, grade III ER+HER2− patients had younger age at diagnosis, more intrinsic luminal B‐like subtypes, invasive ductal carcinomas, larger tumors, greater risk of lymph node metastasis, and a higher chance of receiving chemotherapy.