Second, employing the EpCAM-based CellSearch platform36 for the blood analysis of nine patients with breast cancer, we detected ICAM1+ CTCs in 10–60% of the CTCs (CD45−/cytokeratin+/DAPI+), with a significantly higher proportion of ICAM1+ tumor cells in CTC clusters than in single CTCs (Fig. 2b and Supplementary Fig. 3b–c). This evidence concerns the gene PTPRC and breast cancer.