ERBB2 and breast cancer: Four different breast cancer cell lines (MDA-MB-231, T47D, MDA-MB-453, and SKBR3), that are known to express HER2 at different immunohistochemistry levels (respectively classified as 0, 1+, 2+, and 3+), were spiked in healthy donor blood tubes (7.5 mL) and processed with the CellSearch® (Menarini Silicon Biosystems, Bologna, Italy) for enrichment and the DEPArray NxTTM for single cell selection.