Based on the different cell types, degree of differentiation, and function determining the specificity of keratin expression itself, the epithelial malignant tumors largely retain the specific keratin expression patterns of their corresponding cells of origin even in the epithelial-mesenchymal transition (EMT), in addition to the availability of highly sensitive monoclonal antibodies against K8/K18, the immunohistochemistry of K18 can help identify and diagnose various tumor types (33–35). The gene discussed is KRT18; the disease is carcinoma.