The risk of nodal metastases in breast cancer patients with clinically negative lymph nodes: a population-based analysis.

A population-based study was performed to assess the likelihood of axillary lymph node metastases in patients with clinically negative lymph nodes, according to patient age, tumor size and site, estrogen receptor status, histologic type and mode of detection. Data were obtained from the population-based Eindhoven Cancer Registry. During the period 1984-1997, 7680 patients with invasive breast cancer were documented, 6663 of whom underwent axillary dissection. Of the 5125 patients who were known to have clinically negative lymph nodes and underwent axillary dissection, 1748 (34%) had positive lymph nodes at pathological examination. After multivariate analysis, histologic type, tumor size, tumor site and the number of lymph nodes in the axillary specimen remained as independent predictors of the risk of nodal involvement (P < 0.001). Lower risks were found for patients with medullary or tubular carcinoma, smaller tumors, a tumor in the medial part of the breast and patients with less than 16 nodes examined. This study gives reliable estimates of the risk of finding positive lymph nodes in patients with a clinically negative axilla. Such information is useful when considering the need for axillary dissection and to predict the risk of a false-negative result when performing sentinel lymph node biopsy.