Disseminated and circulating tumor cells in bone marrow and blood of breast cancer patients: properties, enrichment, and potential targets

Introduction From the early days of pathology back in the nineteenth century until now, there has been an ongoing search for the missing link between solid tumors such as breast cancer and distant metastases, which sometimes occur many years after removal of the primary tumor. The “seed and soil” theory hypothesizes the early dissemination of occult tumor cells into blood or bone marrow, which can persist in a dormant state for a long time and then become precursors of metastases in distant organs which offer appropriate conditions.