Expression and prognostic significance of CK19 in canine malignant mammary tumours

Expression of the luminal cytokeratin CK19 was examined in 102 canine mammary carcinomas by immunohistochemical analysis and associated with known expression of oestrogen receptor (ER), basal/myoepithelial cell markers, proliferation and survival. Negative staining for CK19 was present in 23.5% of tumours and was associated with histological type, grade, invasiveness, Ki67 index and expression of basal/myoepithelial cell markers. Positive staining for CK19 was associated with ER expression. Reduced expression of CK19 was associated with both shorter overall and disease-free survival rates; however, CK19 was not an independent prognostic factor in multivariate analysis. Reduced expression of CK19 in canine mammary carcinomas is related to an aggressive phenotype and may play a role in tumour progression.