EGFR and HER2 expression in CTCs from breast cancer patients. (a) Representative images of confocal laser scanning microscopic sections of PBMC cytospins stained with pancytokeratins A45 B/B3 (green) and EGFR anti-rabbit (red) antibodies, showing consecutive scanning sections from the upper cytoplasmic region toward the basal attachment site in step sizes of 0.8 μm (magnification: 600×). (b) Representative images of a cytospin, double stained with monoclonal pancytokeratin (A45-B/B3; green) and polyclonal EGFR anti-rabbit (red) antibodies (magnification: 600×). Also shown is quantification of EGFR and CK co-expression in adjuvant and metastatic CTCs. (c) Representative image of cytospin, double stained with polyclonal pancytokeratin and monoclonal HER2 (green) antibodies (magnification: 600×). Quantification of HER2 and CK co-expression in adjuvant and metastatic CTCs. CK, cytokeratin; CTC, circulating tumor cell; EGFR, epidermal growth factor receptor; HER, human epidermal growth factor receptor; PBMC, peripheral blood mononuclear cell.