Objective This study was to detect micrometastases in the axillary lymph nodes in primary breast cancer patients and investigate its clinical significance. Methods The cytokeratin 19 gene expression was examined by RT-PCR and Southern hybridization methods. The sensitivity was compared with that of immunohistochemistry(IHC) method.Results The sensitivity was 1∶5?105, 1∶106 and 1∶5?104 by RT-PCR, Southern hybridization and IHC methods,respectively. Thirty-five of 170 routine pathology negative lymph nodes (206%)in 52 primary breast cancer patients contained CK-19 positive signals. Twenty-one out of 33(636%) routine negative lymph nodes were found micrometastases positive in 17 patients who proved to be with lymph node metastases by routine pathologic examination.Eleven out of 35(314%) metastasis negative patients by routine pathology were CK-19 gene positive.Hence the micrometastasis found by our method is an independent parameter.Conclusion RT-PCR method, using CK-19 as a biological marker,was sensitive and specific in detecting micrometastases in primary breast cancer,it could be a new prognostic parameter for breast cancer patients.

The rat anti-HRP McAbs were prepared with rat-rat hybridoma and the rat McPAP complex was made by conjugating this McAb with HRP. The results of the present work indicated that the rat MePAP can be used for detection of antibodyantigen reaction by immunohistochemical techniques and ELISA. In both assay it gave strong staining reaction for positive antigen and with background staining appeared very pale. The sensitivity of rat McPAP and HRP labelling rabbit anti-rat IgG has been compared.