Breast cancer metastasis is a complex process where cancer cells spread from the primary tumor to distant organs. Current prognostic markers for breast cancer are not always accurate in predicting the risk of metastasis, leading to unnecessary treatments for many patients. New molecular technologies, such as DNA microarrays, suggest that metastatic capacity might be an inherent feature of breast tumors, challenging the traditional model of metastasis as a late, acquired event. Gene-expression signatures of primary breast tumors can more accurately predict which patients are at risk of developing metastatic cancer and may benefit from adjuvant therapy. These signatures also help identify new therapeutic targets. The traditional model of metastasis, which suggests that metastatic capacity is acquired late in tumorigenesis, is being challenged by new data showing that metastatic capacity might be inherent. The metastatic process involves the ability of cancer cells to invade surrounding tissue, enter the bloodstream, and form new tumors in distant organs. The risk of metastasis increases with lymph-node metastasis, larger primary tumors, and loss of histopathological differentiation. New prognostic markers, such as ERBB2 and PAI1, have been identified, but their prognostic value is still being evaluated. The detection of disseminated tumor cells in peripheral blood, bone marrow, and lymph nodes may provide valuable information for prognosis. Gene-expression profiling has revealed distinct subtypes of breast cancer, each with different prognostic implications. The 70-gene expression profile and the 76-gene signature have shown promise in predicting metastasis risk and patient outcomes. These models suggest that metastasis is an intrinsic property of certain breast tumors, and that the metastatic capacity of breast tumors may be determined by the presence of cancer stem cells. The integration of these findings into a new model of breast cancer metastasis suggests that metastasis is a complex process involving the interaction between cancer cells and the tumor microenvironment. Future research aims to develop more accurate prognostic markers and improve the treatment of breast cancer.Breast cancer metastasis is a complex process where cancer cells spread from the primary tumor to distant organs. Current prognostic markers for breast cancer are not always accurate in predicting the risk of metastasis, leading to unnecessary treatments for many patients. New molecular technologies, such as DNA microarrays, suggest that metastatic capacity might be an inherent feature of breast tumors, challenging the traditional model of metastasis as a late, acquired event. Gene-expression signatures of primary breast tumors can more accurately predict which patients are at risk of developing metastatic cancer and may benefit from adjuvant therapy. These signatures also help identify new therapeutic targets. The traditional model of metastasis, which suggests that metastatic capacity is acquired late in tumorigenesis, is being challenged by new data showing that metastatic capacity might be inherent. The metastatic process involves the ability of cancer cells to invade surrounding tissue, enter the bloodstream, and form new tumors in distant organs. The risk of metastasis increases with lymph-node metastasis, larger primary tumors, and loss of histopathological differentiation. New prognostic markers, such as ERBB2 and PAI1, have been identified, but their prognostic value is still being evaluated. The detection of disseminated tumor cells in peripheral blood, bone marrow, and lymph nodes may provide valuable information for prognosis. Gene-expression profiling has revealed distinct subtypes of breast cancer, each with different prognostic implications. The 70-gene expression profile and the 76-gene signature have shown promise in predicting metastasis risk and patient outcomes. These models suggest that metastasis is an intrinsic property of certain breast tumors, and that the metastatic capacity of breast tumors may be determined by the presence of cancer stem cells. The integration of these findings into a new model of breast cancer metastasis suggests that metastasis is a complex process involving the interaction between cancer cells and the tumor microenvironment. Future research aims to develop more accurate prognostic markers and improve the treatment of breast cancer.