CD44 and breast cancer: We amplified mRNAs from 3D CTC tumorspheres obtained from breast cancer patients with or without BCBM, and analyzed them by RT-PCR to assess expression levels of neoplastic (uPAR/int β1), tumor epithelial (EpCAM), circulating endothelial (CD31), mesenchymal stem cell (CD73, CD90 and CD103) and breast cancer stem cell (CD44+/CD24−) markers.