Immumomagnetic separation of CTCs. Representative confocal laser scanning micrographs of cytospins after immunomagnetic separation of CTCs with EpCAM antibody. Cell cytospins were double stained with EGFR antibody and one of the following: HER2, pEGFR, pPI3K, or pAkt antibody. Cytospin were also double stained with HER2 antibody and either pPI3K or pAkt antibodies (magnification: 400×). EGFR is co-expressed with HER2, pEGFR, phospho-PI3K, and pAkt kinase. CTC, circulating tumor cell; EGFR, epidermal growth factor receptor; HER, human epidermal growth factor receptor; PBMC, peripheral blood mononuclear cell; PI3K, phosphoinositide-3 kinase.