ABSTRACT
Circulating tumor cells (CTCs) have been of interest to the medical and research communities for over a century (1). These cells represent an important link to the process of metastasis, and investigators have been interested in using these cells to establish the diagnosis and prognosis of cancer. In addition, these cells are a potential source of biological information that can be used to predict responsiveness to various treatment agents, monitor response to therapy, and provide tissue for further research into the mechanisms of malignant transformation and resistance. CTCs have been documented in multiple epithelial tumor types (2), but the largest body of data comes from studies of women with breast cancer.
