Histopathologic assessment of the sentinel lymph node in breast cancer.

Thorough pathologic examination of the sentinel lymph node (SLN) improves the accuracy of breast cancer staging and reduces the rate of false-negative results. Intraoperative examination of the SLN with cytological or frozen section techniques remains problematic. Diagnostic difficulties encountered on hematoxylin and eosin paraffin sections in general are easily resolved with cytokeratin immunohistochemistry, but the finding of minute metastases may lead to diagnostic and therapeutic dilemmas. Pathologic characteristics of the primary tumor and SLN metastasis determine the risk of non-SLN metastasis in the same lymphatic basin.