The pretreatment diagnosis were synchronous locally advanced bilateral breast cancers: the left breast cancer was defined invasive ductal carcinoma, ER-negative, PgR-negative, and HER2-positive classified as T4bN1M0, stage IIIb, while the right breast cancer was defined invasive ductal carcinoma, ER-positive, PgR-positive, and HER2-negative classified as T4bN0M0, stage IIIb (Table 1). Here, ESR1 is linked to breast cancer.