EpCAM is generally used as anchor protein to enrich CTCs in various approaches [47, 129], CD44 is a marker for cancer stem cells in numerous tumor entities [130] including breast cancer [131], and is involved in metastases formation [132, 133], while CD47 and c-Met had been linked to recurrence and an invasive program of tumor cells [134, 135]. Here, CD44 is linked to breast cancer.