RESUMEN
PURPOSE: About 20% to 30% of patients with node-negative breast cancer die of systemic metastases in 10 years after surgery. This may be due to either early occult systemic spread before node metastasis or occult lymph node metastasis (OLNM) which is undectected by routine pathologic evaluation. The purpose of this study was to assess the incidence and its prognostic significance of OLNM in breast cancer. MATERIALS AND METHODS: Paraffin blocks of axillary lymph nodes from 50 patients with invasive breast carcinoma initially diagnosed as node-negative by routine histological examination were evaluated. All nodes were serially sectioned by 40 pm thickness interval, followed by hematoxylin-eosin (H-E) staining and cytokeratin immunohistochemical staining. RESULTS: OLNM were detected in 6 patients (12%) by immunohistochemical method; in 3 of these 6 patients, it were also detectable by serial sectioning and H-E staining. OLNM correlated with the primary tumor size (r=0.43, p <0.05). During mean follow- up of 57 months, there were 4 systemic recurrences and one death. Of 6 patients with OLNM, 2 had multiple systemic recurrences (33.3%). Of 44 patients without OLNM, in contrast, only 3 had systemic recurrences (6.8%). Five year disease-free survival rates of patients with and without OLNM were 66.7% and 93.0%, respectively (p=0.087). CONCLUSION: These results suggest that about 10% of patients with "node-negative" breast cancer have OLNM, and the presence of OLNM may have marginal prognostic significance. Serial sectioning and cytokeratin immunohistochemical staining of axillary lymph nodes should be considered as a part of the routine histologic examination especially in the patients with a large primary tumor.