MUC1 and neoplasm: Binding to cell surface mucin protein MUC1 increases circulating tumour cell heterotypic adhesion to the blood vascular endothelium (Zhao et al. 2009), and promotes tumour cell–cell homotypic aggregation for the formation of circulating tumour emboli (Zhao et al. 2010) that facilitate tumour cell survival, extravasation and colonization at distant sites.