CK19 is the smallest keratin with a molecular weight of 40-44 kDa.  which is widely distributed in monolayer epithelial cells and many squamous epithelial tissues, and plays an important role in maintaining cell structure and morphology. Its function is related to cell proliferation, differentiation, invasion and metastasis, and cell cycle, etc. CK19 is an important biomarker of breast cancer cells, lymph nodes, peripheral blood and bone marrow tumor cells.  The keratin of CK10 with molecular weight of about 60kD is not expressed in epidermal basal cells under normal conditions. When the cells generated by basal cell division undergo neoplasia, CK1 / CK10 begins to be expressed.  The expression of CK10 is correlated with the differentiation degree of malignant keratinocytes, and the higher the positive expression in tissues, the stronger the differentiation represented by CK10.