Cytokeratin 8 & 18 (B22.1 & B23.1)

Cytokeratins 8 & 18 (CK 8 & 18) can be found in most simple epithelia, e.g. thyroid, breast, gastrointestinal tract, and respiratory tract. Adenocarcinomas and most non-keratinizing squamous carcinomas will stain with anti-CK 8 & 18, but keratinizing squamous carcinomas will not.1,2 This antibody is used when attempting to demonstrate the presence of Paget cells; there is very little keratin 18 in the normal epidermis so this will only stain Paget cells.3 The use of immunostaining facilitates interpretation and has been shown to be more sensitive than genetic analysis in colorectal carcinoma metastases.4