Clinical Significance of Extracapsular Invasion at Sentinel Lymph Nodes in Breast Cancer Patients with Sentinel Lymph Node Involvement

A certain number of patients have extracapsular invasion (ECI) at the sentinel lymph node (SLN), but only a few reports describe its clinical significance. This study aimed to determine the clinical significance of ECI at SLN in breast cancer patients with involved SLN. This study evaluated ECI at SLN in 131 consecutive SLN-positive patients who underwent axillary lymph node dissection between 2003 and 2008 at the National Kyushu Cancer Center with regard to their long-term prognosis and non-SLN metastasis. Of the 131 patients, 46 (35 %) tested positive for ECI at SLN. Of these 46 patients, 61 % (28/46) had non-SLN metastasis compared with 28 % (24/85) in ECI-negative group (chi (2) test; P < 0.001). Multivariate analysis showed that ECI at SLN is significantly predictive for non-SLN metastasis [hazard ratio (HR) 3.2; 95 % confidence interval (CI) 1.4-7.1; P = 0.005]. The 5-year recurrence-free survival (RFS) rates were 71.3 % in the ECI-positive group and 89.9 %in the ECI-negative group (P = 0.001, log-rank test). Cox-regression analysis showed that ECI at SLN independently predicts lower RFS (HR 4.5; 95 % CI 1.8-11.7; P = 0.002). The findings show that ECI at SLN is an independent predictor of both non-SLN metastasis and poor prognosis for breast cancer patients with involved SLN. The clinical significance of ECI at SLN in operable-stage breast cancer warrants further study.