EPCAM and carcinoma: Recent studies have investigated the use of surface antigens for CTC enrichment and tumour typing: epithelial cell adhesion molecule (EpCAM) is ubiquitously expressed on the surface of epithelial carcinomas and remains the most commonly used marker for enriching and detecting CTCs of breast [39], colon [40] and prostate [41] origins; membrane-bound mucin (MUC1) has been used to detect CTCs of breast [42] and ovary carcinomas [43]; and the ephrin receptor (EphB4) is strongly over-expressed in advanced head and neck cancers [44].