Cytokeratin 18 antibody (CK18) [DC10] is a 45 kDa acidic intermediate filament protein. It is normally co-expressed with Cytokeratin 8 and is found in most simple ductal and glandular epithelia. Studies have shown that this antibody reacts with a wide variety of simple epithelia such as gastrointestinal tract, lung, breast, pancreas, ovary and thyroid tumors, whereas tumor cells of non-epithelial origin such as glioma, melanoma and osteosarcoma are not reactive. It also does not react with stratified squamous epithelium on most squamous cell carcinoma.