Relevance of the immunohistochemical expression of cytokeratin 8/18 for the diagnosis and classification of breast cancer.

PURPOSE The aim of our study was to characterize and describe the different immunohistochemical expression patterns of cytokeratin 8/18 (CK8/18) in breast tumors and to make a correlation between histopathology, immunohistochemistry for CK8/18 and its possible diagnostic value of this pair of keratins for molecular classification of breast cancers. MATERIAL AND METHODS Forty cases of breast tumors immunostained with monoclonal antibodies against CK8/18 using a polymer based detection system and diaminobenzidine as chromogen were microscopically evaluated in normal and tumor breast tissue concerning the intensity, distribution and density of positive cells. Association with histopathology and nuclear grade were also studied. RESULTS Three different models of positive reaction were found: (1) normal cytoplasmic with intense and diffuse pattern, (2) aberrant membrane pattern and (3) aberrant cytoplasmic granular pattern associated with membranous positive reaction. Normal expression of CK8/18 was found in 23 cases of breast cancer, aberrant membranous in nine cases and aberrant with granular pattern in four cases. Further studies will be needed to elucidate these differences and possible correlation with other molecular markers.