Breast cancer is the second leading cause of cancer deaths among women in the United States. Many of these deaths occur when there is an initial diagnosis of invasive or metastatic disease. A protein called NEDD9 has been linked to tumor invasion and metastasis in a variety of cancers. Researchers have now shown that NEDD9 plays a surprising role in the early stages of breast tumor development by controlling the growth of progenitor cells that give rise to tumors.