Histologic detection and clinical implications of micrometastases in axillary sentinel lymph nodes for patients with breast carcinoma.

BACKGROUND: Sentinel lymph node (SLN) biopsy is used increasingly in patients with clinically lymph node negative, early-stage breast carcinoma, because it can spare axillary dissection when the sentinel lymph nodes are negative. The question arises, however, whether complete axillary lymph node dissection (ALND) also is necessary in patients with only micrometastases (< or = 2 mm in greatest dimension) in axillary SLNs. The authors carried out the current study to ascertain the risk of non-SLN axillary metastases in such patients and to assess the detection rate of SLN micrometastases in relation to the sectioning interval and the number of sections examined. METHODS: The authors examined 109 patients with micrometastatic SLNs from a series of 634 patients with carcinoma of the breast who underwent SLN biopsy and complete ALND as part of the surgical treatment for their disease. The SLNs were sectioned completely at 50-microm intervals, and the sections were examined intraoperatively. RESULTS: The overall frequency of metastases in axillary non-SLNs was 21.8%. The frequency was correlated significantly with the size of the SLN micrometastatic focus (P = 0.02): 36.4% of patients with foci > 1 mm had metastases in axillary lymph nodes--a percentage approaching 44.7% of patients with macrometastatic SLNs--whereas only 15.6% of patients with micrometastases < or = 1 mm had other involved axillary lymph nodes. CONCLUSIONS: Outside of clinical trials, patients with T1 and small T2 breast carcinoma and micrometastatic SLNs should undergo complete ALND for adequate staging. However, patients with SLN micrometastases up to 1 mm in greatest dimension have a significantly lower risk of additional axillary metastases, raising the question of whether ALND may be avoided in this subgroup of patients.