Identification and biologic significance of micrometastases in axillary lymph nodes in patients with invasive breast cancer

Context. - The presence or absence of metastases in axillary lymph nodes is one of the most important prognostic factors for patients with breast cancer. During the past decade sentinel lymph node (SLN) biopsy has been increasingly adopted as a minimally invasive staging alternative to complete axillary node dissection. Objective. - Sentinel lymph nodes are more likely to contain metastases than non-SLNs. In routine clinical practice SLNs are assessed by diverse methodologies including multiple sectioning, immunohistochemical staining, and molecular diagnostic tests. Despite the lack of standard histopathologic protocols during the years detailed evaluation of SLNs has resulted in an increased detection of small (micro) metastases. Data Sources. - Breast cancer with micrometastases constitutes a heterogenous group of tumors with variable clinical outcome regarding the risk of additional metastases in the remaining axillary lymph nodes and to patients' survival. Conclusion. - The clinical significance of micrometastases has been subject to great controversy in patients with breast cancer. In this review we highlight controversies regarding micrometastases especially in relation to SLNs.