Cytokeratin 5/6

CK 5/6 is a marker of basal / myoepithelial cells, and therefore is often used to make a diagnosis for triple negative breast carcinoma. It can also be used to distinguish breast usual duct hyperplasia (UDH) and papillary lesions (mosaic-like pattern) from DCIS (usually negative, rarely diffusely positive). CK 5/6 can also separate epithelioid mesothelioma (pos in 83%) from lung adenocarcinoma (neg in 85%) and can be used for differentiating lung adenocarcinoma from lung squamous carcinoma or lung adenosqamous carcinoma, especially when morphology is not well presented. It may also be used in conjunction with P63 to identify squamous origin in a poorly differentiated metastatic carcinoma.