Circulating tumor cells (CTCs) originate from the primary tumor mass and enter into the peripheral bloodstream. Compared to other “liquid biopsy” portfolios such as exosome, circulating tumor DNA/RNA (ctDNA/RNA), CTCs have incomparable advantages in analyses of transcriptomics, proteomics, and signal colocalization. Hence, CTCs hold the key to understanding the biology of metastasis and play a vital role in cancer diagnosis, treatment monitoring, and prognosis. Size-based enrichment features are prominent in CTC isolation. It is a label-free, simple and fast method. Enriched CTCs remain unmodified and viable for a wide range of subsequent analyses. In this review, we comprehensively summarize the differences of size and deformability between CTCs and blood cells, which would facilitate the development of technologies of size-based CTC isolation. Then we review representative size-/deformability-based technologies available for CTC isolation and highlight the recent achievements in molecular analysis of isolated CTCs. To wrap up, we discuss the substantial challenges facing the field, and elaborate on prospects.

循环肿瘤细胞（CTC）起源于原发肿瘤块，并进入外周血流。与外泌体，循环肿瘤DNA / RNA（ctDNA / RNA）等其他“液体活检”组合相比，CTC在转录组学，蛋白质组学和信号共定位分析方面具有无与伦比的优势。因此，CTC是了解转移生物学的关键，并且在癌症诊断，治疗监测和预后中起着至关重要的作用。基于大小的富集功能在CTC隔离中很突出。它是一种无标签，简单，快速的方法。富集的四氯化碳在许多后续分析中均保持不变且可行。在这篇综述中，我们全面总结了CTC和血细胞之间大小和可变形性的差异，这将有助于基于大小的CTC分离技术的发展。然后，我们回顾了可用于CTC分离的具有代表性的基于尺寸/变形性的技术，并重点介绍了在分离CTC分子分析中的最新成就。最后，我们讨论了该领域面临的重大挑战，并详细阐述了前景。