EPCAM and neoplasm: In contrast, HPMCs were negative for the epithelial marker EpCAM which was expressed on the plasma membranes of the Caco2 cells (Fig. 3, bottom panels, red signal) and for the tumor marker carcinoembryonic antigen CEA, whose signal was visible either in intracellular spots or on the cell surfaces (Fig. 3, bottom panels, green signal).