Liquid biopsy is a convenient, fast, non-invasive and reproducible sampling method that can dynamically reflect the changes in tumor gene expression profile, and provide a robust basis for individualized therapy and early diagnosis of cancer. Circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs) are the currently approved diagnostic biomarkers for screening cancer patients. In addition, tumor-derived extracellular vesicles (tdEVs), circulating tumor-derived proteins, circulating tumor RNA (ctRNA) and tumor-bearing platelets (TEPs) are other components of liquid biopsies with diagnostic potential. In this review, we have discussed the clinical applications of these biomarkers, and the factors that limit their implementation in routine clinical practice. In addition, the most recent developments in the isolation and analysis of circulating tumor biomarkers have been summarized, and the potential of non-blood liquid biopsies in tumor diagnostics has also been discussed.

液体活检是一种方便、快速、无创、重复性好的采样方法，可以动态反映肿瘤基因表达谱的变化，为癌症的个体化治疗和早期诊断提供坚实的依据。循环肿瘤DNA (ctDNA) 和循环肿瘤细胞(CTC) 是目前批准用于筛查癌症患者的诊断生物标志物。此外，肿瘤源性细胞外囊泡 (tdEV)、循环肿瘤源性蛋白、循环肿瘤 RNA (ctRNA) 和荷瘤血小板 (TEP) 是液体活检中具有诊断潜力的其他成分。在这篇综述中，我们讨论了这些生物标志物的临床应用，以及限制其在常规临床实践中实施的因素。此外，还总结了循环肿瘤生物标志物分离和分析的最新进展，并讨论了非血液液体活检在肿瘤诊断中的潜力。