CD44 and breast cancer: We applied multiparametric flow cytometry and CD45−/CD44+/CD24− as initial selection markers and specific criteria for EpCAM-positive and EpCAM-negative CTCs: EpCAM-negative PBMCs derived from breast cancer patients sorted through multiparamteric flow cytometry followed by the selection of uPAR/int β1 combinatorial CTC subset expression (Fig. 1).