Interestingly, it has been recently published that CTCs may lose EpCAM during epithelial-mesenchymal transition (EMT) [8, 9], and only EpCAM-negative CTCs (such as breast cancer CTCs) possess enhanced potential to metastasize to the brain [12], suggesting expression of EpCAM may be down-regulated or absent in association with cancer progression and metastasis [12, 13]. Here, EPCAM is linked to breast cancer.