Host-tumor interactions in the progression of breast cancer metastasis.

The dissemination of cells from a primary tumor, resulting in the progressive growth of metastatic carcinoma in distant sites, including bone, lungs, liver and brain, is the most common cause of death of breast cancer patients. The results of studies using rodent tumors and human cancer cell lines, combined with clinical observations, suggest that metastasis is not a random event. It is the result of a sequence of selective events, many of which involve interactions with elements of the microenvironment of the primary and the metastatic tumors. A greater understanding of the metastatic phenotype from cellular and molecular analyses will provide a rationale approach for controlling this most lethal aspect of breast cancer.