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.