Specificity: Ep-Cam (also called ESA, EGP40, 17-1A antigen, KSA, GA7333-2) is a 40kD epithelial protein expressed on baso-lateral cell surfaces in very many epithelial tissues (but absent from mesothelial tissues). The extracellular domain has a cysteine-rich repeat and a small domain with homology to nidogen. It is a homophyllic cell-cell adhesion molecule, recently called Ep-CAM (Litvinov et al., 1994). It reacts with most epithelial cells and carcinomas.