 Abstract cancer cells that have detached from the original tumor and entered the bloodstream are known as circulating tumor cells, CTCs. These rare cells offer a unique opportunity to study the metastatic process and provide valuable information about the disease. Technological advances have made it possible to detect and analyze CTCs, which has led to a better understanding of how they behave and how they may be targeted for therapeutic intervention. This article reviews current methods for detecting and analyzing CTCs, including those based on molecular markers, epithelial to mesenchymal transition, and single-cell sequencing. Additionally, the article discusses the clinical applications of CTCs, such as monitoring response to therapy and predicting patient outcomes. This article was authored by Dan Feng Lin, Les Anxion, Meng Luo, and others.