Precision medicine aims to improve healthcare by identifying subsets of patients that are more likely to benefit from specific treatment strategies. Liquid biopsy offers the unique potential to better understand and monitor disease biology, since it is not burdened by the temporal and spatial limitations of tissue biopsy. CTC (circulating tumor cell) characterization is being explored as an alternative and flexible tool to identify predictive and prognostic biomarkers thanks to its capability of recapitulating a complete biological system. The present chapter will summarize the current clinical applications of CTC enumeration and its combination with other liquid biopsy technologies such as ctDNA. It will, moreover, offer new insights on non-canonical CTCs, which are emerging as a new entity with respect to epithelial circulating cells, and emerging multi-omics essays that may evolve into new comprehensive profiling workflows.
