Circulating Tumor Cells in Breast Cancer

Breast cancer is a heterogeneous disease, with many subtypes with differing tumor biology that has an impact on its metastatic potential. Breast cancer metastasis is driven by genetic and/or phenotypic changes that occur in tumor cells, allowing them to leave primary site and spread through the body via the circulatory system. These circulating tumor cells (CTCs) may extravasate at secondary site and form metastases. The recent advent of new techniques, enabling the detection, enumeration, and characterization of CTCs in patients, has opened new possibilities for diagnostics and treatment, as well as research of the heterogeneity and molecular profile of these tumor cells. Although CTCs in breast cancer are relatively well studied and their prognostic value is proven, there are still many unanswered questions, especially regarding how this information may be used in clinical practice. CTC research holds the promise that it will provide tools for an accurate prognosis and early detection of metastatic disease, resulting in an appropriate change of treatment.