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).
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12. Laakso M, et al. Cytokeratin 5/14-positive breast cancer: true basal phenotype confined to BRCA1 tumors. Mod Pathol. 2005; 18:1321-8.
13. Bhargava R, et al. CK5 is more sensitive than CK5/6 in identifying the “basal-like” phenotype of breast carcinoma. Am J Clin Pathol. 2008; 130:724-30.
14. Jain RK, et al. Atypical ductal hyperplasia: interobserver and intraobserver variability. Mod Pathol. 2011; 24:917-23.
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