EPCAM and head and neck cancer: Co-expression pattern of pan-CK and EpCAM epithelial markers was considered as one of the signs of epithelial–mesenchymal plasticity (EMP) or partial-EMT, based on published data on head and neck cancer that retention of cytokeratin expression combined with gradual loss (or keeping at lower level) of EpCAM expression was the evidence of the processes constituting tumor EMP [16,69].