Cytokeratins

Concept

A type of intermediate filaments. They are major structural proteins in the cytoplasm of normal epithelia.

Types

Al least there are 20 different types (excluding trichocytic keratins from hair and nails). They are numbered from 1 to 20.

CK1 to CK8: high mollecular weight type II cytokeratins, neutral-basic.

CK9 to CK20: low mollecular weight, acidic type I cytokeratins.

CKs are always paired (a basic plus an acidic, forming a heterodimer complex).

Simple epithelia: mainly CK8 and CK18.

Stratified epithelia: mainly CK5 and CK14.

Detection of CKs by immunohistochemistry:

34betaE12 (CK903): CK1, CK5, CK10, CK14. They are found in complex epithelia. They ususally stain squamous and ductal epithelia, myoepithelial cells and squamous cell carcinoma.

CAM 5.2: CK7 and CK8. Usually, it stains nonsquamous epithelium, including eccrine ductal epithelium.

PKER: several keratins of hight mollecular weight. It stains various cells of epithelial origin, all epidermal layers of the skin, skin adnexa, squamous cell carcinoma and basal cell carcinoma.

AE1/AE3: cocktail of low and hight mollecular weight keratins (CKs 1 to 10, 13 to 16, and 19).