The breast cancer represents one of the most prevalent cancers in the world. The outlook for patients diagnosed with breast cancer has been changing for the better over time, with several significant advances coming through in the past 10 years; among them, and after highlighting the importance of prevention and early diagnosis, relevant advances as a better understanding of the process through gene expression analysis, at the ability to use specific therapeutic targets, and a more advanced hormonal therapy played a more than significant positive role. Nevertheless, and despite the above mentioned improvements in treatment and prevention, breast cancer remains one of the leading causes of cancer mortality in women.
Approximately 90% of cancer mortality is due to the development of metastatic disease. The metastatic process involves the discharge of tumor cells from the primary tumor into peripheral blood (circulating tumor cells, CTCs) to a target organ. Recently, the clinical implication of detection of CTCs in breast cancer has been recognized and accepted.