Clinical significance of occult micrometastases in axillary lymph nodes in "node-negative" breast cancer patients

The most important subgroup of breast cancer patients for whom reliable prognostic indicators are needed is women without axillary lymph node metastases. We evaluated the clinical significance of occult micrometastases in axillary lymph nodes in 148 consecutive "node-negative" breast cancer patients. The median age of the patients at surgery was 52 years and the median follow-up period after surgery was 98.5 months. Occult micrometastases were detected in 21 of 148 patients (14.2%) by means of immunohistochemical analysis using AE1/3 antibody and a single unstained section after routine histo pathological examination. Log-rank tests indicated that the 7-year disease-free survival (DFS) and overall survival (OS) rates by Kaplan-Meier methods were significantly better in patients without occult micrometastases than in patients with occult micrometastases [DFS, 93% versus 71% (P=0.0009); OS, 96% versus 76% (P=0.0001)]. According to Cox's multivariate analysis, the presence of occult micrometastases had the most significant effect on DFS (P=0.0053) and OS (P=0.0035). These findings suggest that the presence of occult micrometastases is an independent and significant predictor of clinical outcome, and that their immunohistochemical detection after routine histopathological examination is useful for selecting the "node-negative" breast cancer patient subgroup at high risk for relapse and death.