EPCAM and carcinoma: Today, we know that EpCAM is present as a heart-shaped cis-dimer at the cell surface2, and that it has a broader but nevertheless sharply restricted expression pattern in undifferentiated pluripotent embryonic stem cells (ESC)3–5, hepatic, pancreatic epithelial and other endodermal progenitor cells6–8, epithelium9, carcinoma and cancer stem cells10,11.