ESR1 and breast cancer: The univariate analysis showed that the histologic grade (P = 0.010), number of positive SLNs (P < 0.001), number of negative SLNs (P < 0.001), number of SLNs dissected (P < 0.001), SLN metastasis ratio (P < 0.001), LVI status (P < 0.001), ER status (P = 0.011), HER2 status (P = 0.005), molecular subtype (P = 0.001), and RS (P < 0.001) were associated with NSLN involvement in breast cancer patients with 1–2 positive SLNs (Table 1).