Cytokeratin 4 also known as Keratin 4, CK4,  KRT4 is a member of the keratin gene family. Cytokeratin 4 plays a crucial role in maintaining the structural integrity of epithelial cells, particularly in the differentiated layers of mucosal and esophageal epithelia, where Cytokeratin 4 contributes to the mechanical resilience and barrier function of these tissues. Cytokeratin 4 is part of the cytokeratin family, which consists of intermediate filament proteins that provide support and shape to epithelial cells. The expression of Cytokeratin 4 is particularly important as Cytokeratin 4 serves as a marker for epithelial differentiation and can aid in the diagnosis of various epithelial malignancies.