Micrometastases in Sentinel Lymph Nodes: Not Getting Lost in Translation

Abstract

Advances in technology have led to increasingly minimally invasive procedures and an increased ability to detect very small amounts of disease. With sentinel lymph node (SLN) biopsy, initial concerns about false-negative results are now balanced with concerns of clinical false-positive results, defined as instances when small amounts of disease have no downstream clinical consequences. The evolution in carefully defining what constitutes clinically meaningful disease and necessary treatments is nicely illustrated in breast cancer. SLNs are considered positive if tumor cells meet a size threshold of 0.2 mm or 200 cells, although disease that is detected by cytokeratin immunohistochemistry alone (without confirmatory hematoxylin and eosin staining) still has somewhat unclear implications. Further, even in the setting of unequivocal disease in SLNs, there are increasing data to support not completing an axillary lymph node dissection (ALND). Most notably, practicechanging results from the American College of Surgeons Oncology Group Z0011 trial effectively demonstrated that ALND did not significantly affect overall or disease-free survival, heralding excellent locoregional control from multimodality treatment of patients with T1/2 invasive breast cancer and positive SLNs who are treated with lumpectomy, radiation therapy (including the low axilla), and adjuvant systemic therapy. 1