{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Cytokeratin 4 is a type II cytokeratin and is specifically found in differentiated layers of the mucosal and esophageal epithelia together with Cytokeratin 13. Mutations in the genes encoding this protein (KRT4) have been associated with White Sponge Nevus, characterized by oral, esophageal, and anal leukoplakia."}]},{"type":"paragraph","children":[{"type":"text","value":"A decreased expression of CK4 is associated with head and neck squamous carcinoma. It is helpful in the differentiation of squamous cell carcinoma of esophagus origin from that of thyroid origin."}]}]}