Table 1.

Examples of recent investigations of CTC clusters biology. The table summarizes recent literature on homotypic and heterotypic CTC clusters, as well as it indicates some of the major take-home messages of these selected studies.

CTC cluster type	Major findings	References
Homotypic	Physical entrapment of CTC clusters in capillary beds	[13,43]
	Correlation of CTC clusters with bad prognosis	[[24], [25], [26], [27],29,30,37]
	Elevated metastatic ability of CTC clusters	[24,35]
	Molecular cell–cell adhesion mechanisms supporting CTC clusters	[24,35,38,39]
	Epigenetic features and vulnerabilities of CTC clusters	[38]
Heterotypic	CTC-myeloid cell clusters are endowed with a high metastatic ability	[36,44]
	IL-1β and IL6 are critical cytokines for CTC-neutrophil crosstalk	[36]
	CTCs interact with additional stromal cells, such as fibroblasts and platelets	[48,50]