ESR1 and metastatic malignant neoplasm in the lymph nodes: Statistical analysis revealed significant differences (P < 0.05) among female patients diagnosed with breast cancer having distinct postoperative recurrence risks in the following indicators: the number of lymph node metastases, lesion size, histological grading, vascular tumor embolus, nerve invasion, ER expression, PR expression, HER-2 expression, proliferation marker (Ki-67) expression, molecular typing, clinical staging, and ultrasound image characteristics (blood flow, mass morphology, mass margins, lymph node morphology, internal calcification) (refer to Table 1).