Predictive Value of Tumor Load in Breast Cancer Sentinel Lymph Nodes for Second Echelon Lymph Node Metastases

BACKGROUND The need for routine axillary lymph node dissection (ALND) in patients with invasive breast cancer and low-volume sentinel node (SN) involvement is questionable. Accurate prediction of second echelon lymph node involvement could identify those patients most likely to benefit from ALND. METHODS A consecutive series of 317 patients with invasive breast cancer and a tumor positive axillary SN followed by ALND was reviewed. Clinicopathologic features of the primary tumor and the SN were assessed as possible predictors of second echelon lymph node involvement. RESULTS Second echelon metastases were found in 116/317 cases (36.6%). Frequency of second echelon lymph node involvement in patients with isolated tumor cells (ITC, N=23), micro- (N=101) and macrometastases (N=193) was 13%, 20% and 48%, respectively (p<0.001). Based on the area % of SN occupied by tumor no subgroup of patients could be selected with less than 20% second echelon lymph node involvement. However, none of the patients with SN ITC or micrometastases and a primary tumor size </=1 cm (N=12, 3.8%) had second echelon lymph node involvement. CONCLUSIONS Accurately measured SN tumor load predicts second echelon lymph node involvement. However, even in patients with ITC, the second echelon lymph nodes are involved in 13% justifying ALND.