CTC roles in cancer and liquid biopsy. (A), CTCs are shed by tumors and disseminate through the bloodstream, holding potential to establish metastases. Their intrinsic traits, coupled with interactions within the microenvironment, significantly influence their metastatic proficiency. CTCs exhibit resistance against anoikis, utilize EMT for enhanced migration, and adeptly subvert immune surveillance. The timing of blood sampling crucially impacts the yield of detectable CTCs; (B), CTCs serve as pivotal elements in liquid biopsies, offering diverse clinical utilities in precision medicine endeavors, ranging from diagnostics to treatment response assessment, thus propelling the realm of personalized medicine forward.