Breast Cocktail (CK HMW/p63 + CK7/8/18) is comprised of mouse monoclonal anti-CK HMW and anti-p63 antibodies as well as rabbit monoclonal anti-CK7 and mouse monoclonal anti-CK8/18 antibodies. CK HMW (high molecular weight cytokeratin) is expressed in the cytoplasm of basal cells and myoepithelium of breast tissue (1-4). p63 is a transcription factor present in the nuclei of myoepithelial cells (2,4). In contrast, CK7, CK8 and CK18 are low molecular weight cytokeratins primarily expressed in luminal cells of the breast (1-3).
CK HMW, p63, CK7, CK8 and CK18 have routinely been used as a panel of IHC markers to complement morphological evaluation in the assessment of breast lesions, due to the differential expression of the luminal vs. basal and myoepithelial markers (1-5). Cases of usual ductal hyperplasia (UDH) have been associated with expression of the basal cell markers, intermixed with cells expressing the keratins of luminal cells (1-2, 6-10). Most cases of atypical ductal hyperplasia (ADH) and low grade ductal carcinoma in situ (LG-DCIS) were negative for the basal markers and exhibited an immunophenotype indicative of luminal cells (1,5-8). Additionally, the basal phenotype has been shown to be characterized by luminal expression of the basal and myoepithelial markers, using a cocktail of CK HMW and p63 (11-13).
IHC, using CK HMW, p63, CK7, CK8 and CK18 antibodies, evaluated in combination with hematoxylin and eosin (H&E), has been shown to significantly increase inter-observer agreement amongst pathologists, compared to H&E alone (14).