Two-thirds of the keratin genes are found in the cutaneous epithelium, and the family member Krt14 is mainly expressed in basal cells of epithelial tissues (including the skin, esophagus, salivary glands, small intestine, and mucosa) physiologically50–52 and in poorly differentiated tumor cells pathologically, which form well-defined boundary with connective tissue underneath the basement membrane.53 The properties of Krt14 suggested that the Krt14+Ctsk+ subset possessed epithelial characteristics. The gene discussed is CTSK; the disease is neoplasm.