Micro- and macro-metastasis in the axillary lymph node: A review

Pathologists typically examine the sentinel lymph nodes excised from patients with invasive breast cancer more thoroughly than they have historically those from axillary lymph node clearance specimens. This, it is thought, increases the chances of detecting small metastatic foci (i.e. macrometastases (>2 mm), micrometastases (0.2–2 mm), or isolated tumour cell clusters (<0.2 mm or <200 cancer cells in one section)). However, the clinical significance of these small metastatic deposits remains unclear. Although an increasing nodal burden is known to proportionally decrease patient survival, the American College of Surgeons Oncology Group (ACOSOG) Z0011 trial has, at the least, raised questions as to how best to manage nodal metastasis in early invasive breast cancer. These issues, and a brief overview of the biology of metastatic spread are presented in this review.