Clinical Implications of Micrometastasis Detection in Internal Mammary Nodes of Breast Cancer Patients

BACKGROUND: The aim of this study was to assess the efficiency of step-serial sectioning (SSS) combined with hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining in detecting micrometastasis of internal mammary lymph nodes (IMLNs). PATIENTS AND METHODS: 135 IMLNs from 88 breast cancer patients were re-examined by SSS, combined with either H&E or IHC staining of the biomarkers cytokeratin-19 and epithelial membrane antigen. RESULTS: Of the 135 IMLNs, 6 nodes from 5 cases displayed 1 or more micrometastases. Histological grade and lymphovascular invasion status were significantly correlated with micrometastasis in the IMLNs (p = 0.018 and 0.001, respectively). Of the 6 nodes positive for micrometastasis, 1 node was detected by both H&E and IHC staining. The remaining 5 nodes from 4 cases showed evident tumor cells only by IHC staining. Finally 8 of the 83 patients (9.64%) without IMLN metastasis showed distant metastasis, while 2 of the 5 patients (40%) with IMLN metastasis showed distant metastasis within 28 months of operation. CONCLUSION: SSS combined with H&E and IHC staining is more efficient in detecting micrometastasis than classic routine single-slice H&E only.