Evaluation of three mRNA markers for the detection of lymph node metastases.

The expressions of three mRNA markers were correlated with the results of extensive histopathological examination of a total of 290 axillary lymph nodes from 29 breast carcinoma patients. Included were two established markers for breast cancer (cytokeratin-19 and mammaglobin) and the novel marker DNA methyltransferase 3b (DNMT3b). DNMT3b was significantly overexpressed in breast cancer compared to normal breast tissue. The expression of the three markers in axillary lymph nodes was determined using quantitative real-time RT-PCR. DNMT3b expression showed a specificity of more than 99%, which was comparable to that of cytokeratin-19 and better than that of mammaglobin. The sensitivity of RT-PCR relative to histopathology was highest for cytokeratin-19 (96%), followed by DNMT3b (88%) and mammaglobin (68%). The overall agreement of histological and RT-PCR results was 96-99%. The results indicate that expression analysis of marker genes by quantitative RT-PCR can be a useful tool for lymph node diagnosis in breast cancer.