Circulating tumor cells (CTCs) are emerging as a minimally invasive liquid biopsy capable of providing longitudinal monitoring of tumor progression and response to therapy. Since most cancer-related deaths are caused by distant organ metastasis, understanding this pathway is of great importance in reducing cancer mortality. Metastasis is a multistep process that starts with local invasion (the entry of cancer cells from the primary tumor into the bloodstream). Therefore, vascular circulation is the interface between the primary tumor and the target organ for metastasis, making CTCs a critical driver of metastasis. Thus, functional characterization of CTCs may provide a deep understanding of the biology of metastasis, providing a rich source of potential drug targets and biomarkers for early diagnosis and the prediction of prognosis and therapy response. 

In this special issue, we welcome studies and reviews covering the following topics:

1. Assays for detecting and/or molecular and functional characterization of CTCs.
2. Evaluation of the prognostic values of CTCs in different disease settings.
3. Developing novel CTCs-based assays including early diagnosis, prediction of prognosis, and therapy response. 
4. Molecular and functional studies using CTCs to understand metastasis.
5. CTCs-based Case studies
6. CTCs-based Clinical trials.