It is the object of combined investigations using proteomics and immunohistochemistry techniques, in the pursuit of biomarkers for breast neoplasms, where, primarily, a relationship is observed between the expression of cytokeratins and the epithelial origin of this neoplasm and the relationship between the high expression of keratin 18 and the lower invasiveness of feline mammary carcinomas [76]. Here, KRT18 is linked to breast carcinoma.