CXCR4 and neoplasm: The identification of CXCR4+ tumor cells as metastasis stem cells (MetSCs) (Oskarsson et al, 2014) in colorectal cancer (CRC; Croker & Allan, 2008; Zhang et al, 2012; Murakami et al, 2013; Wang et al, 2014) allowed us to evaluate the clinical relevance of targeting CRC MetSCs by assessing whether their selective elimination induces antimetastatic activity.