The biology of metastatic breast cancer

Early detection and surgical removal of breast cancer are most effective in managing a disease that may affect up to one in ten women in North America and Western Europe. However, one of the most important prognostic indicators for breast cancer is the presence of neoplastic cells in the axillary lymph nodes. The dissemination of cells from a primary lesion, resulting in the progressive growth of metastatic carcinoma in distant sites (including bone, lungs, liver, and brain) is the most common cause of death in breast cancer patients. Experimental studies on the biology of metastatic breast cancer have used rodent tumor systems, and, in recent years, the transplantation of human breast carcinoma cells into athymic mice. The results of such studies, combined with clinical observations, suggest that metastasis is not a random event. The formation of secondary lesions is the result of a sequence of selective events. A better understanding of the metastatic phenotype from cellular and molecular analyses will provide a basis for rational approaches to preventing and treating this most lethal aspect of breast cancer.