EPCAM and neoplasm: Analysis of the exosomes obtained from the plasma of nine HNSCC patients (three in stage pT1, one in stage pT3, and five in stage pT4), all of whom benefited from positive clinical outcomes following treatment, on day 7 or 4–6 weeks after PDT treatment confirmed that the PDT-mediated secretion of exosomes contained E-cadherin, and restored epithelial morphology and epithelial cell adhesion molecule (EpCAM) expression in tumor cells.