 With an estimated 2 million women with undetected breast cancer in the United States, the need for improved early detection is imperative. Early diagnosis for these women is key to minimizing quality life-years lost to disease and optimizing success of treatment. Evidence now exists supporting the finding that systemic spread is an early event in the natural history of breast cancer, manifested as a release of single cancer cells from the incident, clinically undetectable tumor, which circulate through the bloodstream and deposit within remote tissues. Reliable and accurate detection of these circulating tumor cells CTCs is now possible with a simple peripheral venous blood draw. This study hypothesizes that women with CTCs and no other signs of malignancy have clinically undetectable disease. 