ESR1 and breast cancer: Regarding BCSS, tumor size (≤2.0 cm vs >2.0 cm, P = .048), ER status (negative vs positive, P = .006), PR status (negative vs positive, P = .033), and molecular subtypes (non‐TNBC vs TNBC, P = .001) showed significant interactions with vertical orientation in predicting BC‐specific deaths (Figure 2B).