KRT19 and carcinoma of esophagus: It has been reported to be involved in esophageal carcinoma metastasis,[3] and high level of MMP9 expression is associated with lymph node metastasis in esophageal carcinoma.[4] Cytokeratin 19 (CK19) and cytokeratin 20 (CK20) are the principal structural elements of the cytoskeleton of epithelial cells.