This study was designed to elucidate the biology of cancer metastasis and differences in the biologic status between primary tumors and metastatic lymph nodes of invasive breast cancer by comparing the well known prognostic factors p53 gene mutation, p53 protein expression and the MIB-1 index. An additional goal was to investigate the p53 mutational pattern of breast cancer patients.

We used the PCR-SSCP method to detect p53 gene mutation and immunohistochemical staining to establish p53 protein expression and the MIB-1 labelling index in 25 primary tumors and metastatic lymph nodes from breast cancer patients. We then made a comparison the between primary tumors and the metastatic lymph nodes.

The results indicated a correlation between histologic grade and p53 gene mutation as well as p53 protein expression, but showed no correlation to MIB-1 labelling index. The concordance rates of p53 gene mutation and p53 protein expression between the primary tumors and metastatic lymph nodes were 72% and 100%, respectively. Three cases showed a different mutated exon number between the primary tumors and the metastatic lymph nodes. Some cases showed p53 gene mutation only in the primary tumors, but while other cases only in the metastatic lymph nodes. The MIB-1 labelling index increased with tumor grade. The p53 altered group show a higher mean MIB-1 index than the non altered group's in both the primary tumors and metastatic lymph nodes.

p53 gene mutation is not consistent with p53 protein expression and there are some differences in p53 gene mutation between primary tumors and metastatic lymph nodes in breast cancer. Therefore, metastatic tumor have different characteristics from those of primary tumors. In breast cancer, metastasis is regulated not only by an upregulating mechanism but also by a down-regulating mechanism.