In another recent study, in a limited number of five metastatic breast cancer patients with more than 100 CTCs/7.5 mL PB (enumerated using the CellSearch), single EpCAM‐positive CTCs were isolated by DEPArray and compared with matched cfDNA and primary tumor tissue by targeted NGS for about 2,200 mutations in 50 cancer genes; according to this study, in these five patients, cfDNA profiles provided an accurate reflection of PIK3CA mutations seen in individual CTCs (Kidess‐Sigal et al., 2016; Shaw et al., 2017). This evidence concerns the gene PIK3CA and breast cancer.