Pathologic Evaluation of Lymph Nodes in Breast Cancer: Contemporary Approaches and Clinical Implications

The presence of detected metastases in locoregional lymph nodes of women with breast cancer is an important prognostic variable for cancer staging, prognosis, and treatment planning. Systematic and standardized lymph node evaluation with gross and microscopic protocols designed to detect all macrometastases larger than 2.0 mm is the appropriate objective based on clinical outcomes evidence. Pathologists will detect smaller micrometastases and isolated tumor cell clusters (ITCs) by random chance but will also leave similar sized metastases undetected in paraffin blocks. Although these smaller metastases have prognostic significance, they are not predictive of recurrence for chemotherapy naïve patients. Thus, protocols to reliably detect metastases smaller than 2.0 mm are not required or recommended by guidelines. Women with T1-T2 breast cancer with a clinically negative axilla but with 1 or 2 pathologically positive sentinel nodes now have alternative options including observation and axillary irradiation and do not require completion axillary dissection.