Breast cancer sentinel node metastases: histopathologic detection and clinical significance

Lymphatic mapping with sentinel lymphadenectomy (LM/SL) is an accurate and less morbid means of determining the tumor status of the axilla in breast cancer patients than standard level I and II axillary lymph node dissection (ALND). This review addresses the handling and pathologic examination of the sentinel node (SN), the clinical significance of tumor within the SN, and the risk factors for non-SN tumor involvement.

The seminal works that have addressed pathologic examination of ALND specimens and SN specimens are summarized, and the important studies attempting to identify predictors of non-SN metastases in patients with a tumor-involved SN are reviewed.

Standard single-section hematoxylin-eosin (H&E) examination is inadequate for reliable detection of axillary or SN metastases. Large studies appropriately powered to detect a survival difference for patients with micrometastatic disease are reviewed. The current data on the clinical significance of micrometastatic nodal disease is inconclusive. While several strong predictors of non-SN tumor involvement have been identified, none is reliable enough to allow omission of ALND in patients with a tumor-involved SN.

Routine examination of the SN specimen should include serial sections with H&E stain. Ongoing prospective clinical trials should help to define the clinical significance of SN micrometastases. Furthermore, these trials could help identify predictors of non-SN metastasis that would allow a subset of patients with a tumor-involved SN to avoid the morbidity of ALND.