Cytokeratin 18 (CK18) is a type I intermediate filament protein important for various cellular processes like apoptosis, mitosis, cell cycle progression, and signaling. CK18 is found primarily in many single-layered epithelial tissues like the liver, lung, kidney, pancreas gastrointestinal tract, or mammary gland and is localized in the cytoplasm and perinuclear regions. CK18 is regulated by site-specific phosphorylation and functions to provide a flexible intracellular scaffolding to allow the cytoplasm to resist external stresses and maintain normal mitochondrial structure. CK18 is a marker for diagnostic histopathology and is strongly linked to the functional behavior of some tumor cells.

Common detection and analytical techniques include ELISA, flow cytometry, IHC, immunoblotting, SDS-PAGE, Immunoprecipitation, and statistical analysis.