Tanvir Khan in The Scientist:
Breast cancer is the most frequently diagnosed cancer and contributes to 15 percent of all cancer-related deaths in women worldwide. Though 20–30 percent of patients with early-stage breast cancers eventually develop metastatic cancer, few effective treatments for preventing rapid metastatic progression exist.1
Tumor cell motility and invasion are essential drivers of metastasis, as tumor cells must migrate away from the primary tumor and invade new sites. Tumor cells at the primary cancer site promote metastasis by recruiting immunosuppressive inflammatory cells, such as activated macrophages, neutrophils, and myeloid-derived suppressor cells, which facilitate tumor cell migration and survival.
More here.