Circulating tumor cells (CTCs) are cells that have shed into the vasculature or lymphatics from a primary tumor and are carried around the body in the circulation. CTCs thus constitute seeds for the subsequent growth of additional tumors (metastases) in vital distant organs, triggering a mechanism that is responsible for the vast majority of cancer-related deaths. Modern cancer research has demonstrated that CTCs derive from clones in the primary tumor. The significant efforts put into understanding the CTCs biological properties have demonstrated the critical role circulating tumor cells play in the metastatic spread of carcinoma. Furthermore, highly sensitive, single-cell analysis demonstrated a high level of heterogeneity seen at the single cell level for both protein expression and protein localization and the CTCs reflected both the primary biopsy and the changes seen in the metastatic sites. Tissue biopsies are poor diagnostic procedures: they are invasive, cannot be used repeatedly, and are ineffective in understanding metastatic risk, disease progression, and treatment effectiveness. CTCs thus could be considered a “liquid biopsy” which reveals metastasis in action, providing live information about the patient’s disease status.

In the present book, fifteen typical literatures about circulating tumor cells published on international authoritative journals were selected to introduce the worldwide newest progress, which contains reviews or original researches on medical science, oncology, anatomical pathology, biopsy, ect. We hope this book can demonstrate advances in circulating tumor cells as well as give references to the researchers, students and other related people.