Detection of Breast Cancer Micrometastases in Sentinel Lymph Nodes

ABSTRACT

PURPOSE: Axillary lymph node status is a powerful prognostic factor in breast carcinomas. However, patients without axillary lymph node metastases are not completely devoid of risk for relapse. Also, the axillary lymph node micrometastases significantly contribute to the selection of high-risk patients. Recently, sentinel lymph node (SLN) biopsy has been proposed as a potential alternative to full axillary lymph node dissection for staging breast carcinomas. To validate this hypothesis, we evaluated the distribution of occult metastases in sentinel and nonsentinel lymph nodes. METHODS: Twenty patients who had breast carcinomas and who underwent a SLN biopsy followed by an axillary lymph node dissection during March and July 2000 at Seoul National University Hospital were evaluated. Thirty SLNs devoid of metastasis, as determined by hematoxylin and eosin (H&E) staining, were evaluated for micrometastases by pan- cytokeratin immunohistochemistry (IHC) and reverse transcriptase polymerase chain reaction (RT-PCR) using Keratin 19 mRNA and MUC1 mRNA. Nonsentinel lymph nodes (NSLN) were also evaluated by pan-cytokeratin IHC. RESULTS: One out of the 30 SLNs (3.3%) had occult metastases which were identified by IHC and 4 out of the 30 SLNs (13.3%) had occult metastases which were identified by RT-PCR. NSLNs devoid of metastases by H&E staining proved to be free of micrometastases by IHC. CONCLUSION: IHC and RT-PCR are more sensitive methods for detecting micrometastases than conventional H&E staining alone. If an SLN is tumor free by IHC or RT-PCR, we can assume that the remaining lymph nodes in the axilla are also tumor free, consequently, an SLN biopsy can bea substitute for axillary lymph node dissection.