A Note of Caution: Variable Cytokeratin Staining in Sentinel Node Metastases.

Sentinel lymph node biopsy is the current standard procedure used to stage patients with breast cancer. The best histological method in evaluating sentinel nodes is highly debated among institutions and is thus not standardized. The optimal histological analysis is a balance between comprehensive evaluation of the sentinel nodes and cost effectiveness. One commonly used approach is serial sectioning and alternately staining with hemotoxylin and eosin and AE1/AE3 cytokeratin immunohistochemistry analysis. We report 2 cases of metastatic carcinoma demonstrating negative staining for AE1/AE3. This observation highlights a rare but potential pitfall to this commonly used strategy in assessing sentinel lymph node biopsies in breast cancer.