Detection of Lymph Node Micrometastases in Breast Cancer by Using Mammaglobin mRNA RT-PCR

ABSTRACT

PURPOSE: The detection of axillary lymph-node micrometastases (ALNM) in breast cancer by using the reverse transcriptase-polymerase chain reaction (RT-PCR) may provide a good guide for postoperative therapy. Expression of the mammaglobin gene has been noted to be restricted to the mammary gland, and the gene is present at higher levels in breast tumors than in nonmalignant breast tissues. Based on its breast specific pattern of expression, we studied its predictive value for detecting ALNM in breast cancer. METHODS: RT-PCR amplifications of mammaglobin and keratin- 19 were done on 39 lymph nodes collected from 39 breast cancer patients, 25 pathologically node-positive cases and 14 node-negative cases by using H&E staining; then a comparison between both gene expressions of lymph nodes according with the pathological report was done. RESULTS: In the 25 pathologically positive cases, mammaglobin and keratin-19 expressions were positive in 22 cases (88.0%) and 23 cases (92.0%), each. In the 14 pathologically negative cases, mammaglobin and keratin-19 expressions were positive in 5 cases (35.7%) and 7 cases (50%), each. The concordance rate between mammaglobin expression and H&E staining, between keratin-19 and H&E staining, and between mammaglobin expression and keratin-19 expression were 79.5%, 76.9%, and 82.1%, each. In pathologically negative cases, mammaglobin expression was related to larger size (p=0.034), poor nuclear grade (p=0.027) and histologic grade (p=0.077) of primary tumor. CONCLUSION: From the fact that mammaglobin expression is confined to only breast tissues and from the results that the concordance rate between mammaglobin expression and H&E staining is the same as that between keratin-19 and H&E staining, mammaglobin can be used as a marker of breast-cancer ALNM.