Are CK+/CD45+ Double-Positive Circulating Cells of Tumor-origin? Characterization in METAstatic Breast Cancer

A prospective, single-centre, proof-of-concept pilot study in patients with metastatic breast cancers (MBC) (whatever the immunohistochemical subtype) treated at the IUCT-O. Eligible patients will be selected and informed of this study during a medical consultation for cancer that has metastasised, has relapsed or is progressing metastatically, by medical oncologists at the Oncopole Claudius Regaud (OCR). Then, with the patient's agreement and before the start of anti-tumour treatment, a blood sample will be taken to detect DP-circulating cells. A breast cancer tumour sample (non-bone metastasis or, failing that, primary tumour) must be available (FFPE archived tumour block). Each patient will participate in the study for one day. 60 patients will be included in this interventional study.