Furthermore, our flow cytometry analyses of the blood cells from patients with breast cancer demonstrated that, compared to granulocytes and lymphocytes, monocytes express a higher level of SEMA4A (Fig. 5d, and Supplementary Fig. S8c), and that the heterotypic CTC-WBC clusters double positive for EpCAM and CD45 have enriched co-expression of PLXNB2 and SEMA4A versus WBC-only clusters and single cells (Fig. 5e, Supplementary Fig. S8d-e), implying the possible contribution of PLXNB2 and SEMA4A to heterotypic CTC-WBC clustering. Here, EPCAM is linked to breast cancer.