摘要The presence of lymph nodes and bone marrow micrometastases of patients with breast carcinoma by immunohistochemistry (IHC) methods has been strongly correlated to early recurrence and shorter overall survival. The aim of this study was to detect micrometastases in matched sample pairs of lymph nodes and the bone marrow of primary breast cancer patients using a more sensitive method, and compare with other clinical parameters. Methods: Cytokeratin 19 (CK-19) gene mRNA expression was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot hybridization. Human breast cancer cell line T47D was mixed with bone marrow cells at different proportions. The positive detection rate was compared among RT-PCR, Southern blotting and IHC methods. Results: Cytokeratin 19 gene was expressed in all 6 positive control samples, while the expression wasn't seen in 18 negative control samples. CK-19 IHC positive cells were detected at a dilution of one T47D cell in 5×105 bone marrow cells, while the sensitivity detected by PCR and Southern blot hybridization was at 1:5′ 104 and 1:106, respectively. In the samples from the 35 patients, we found CK-19 positive cells in 2 cases (5.7%) by IHC. CK-19 gene expression signal was detected in 14/35 (40%) by RT-PCR,and 17/35 (48.6%) by southern blotting. Four cases were micrometastases positive both in lymph node and bone marrow (11.4%). There was no correlation between CK-1 9 detection and other clinical parameters. Conclusion: combined detection of micrometastases in lymph node and bone marrow by RT-PCR and Southern blotting, using CK-19 as a biological marker, is a highly sensitive method for breast cancer.