Keratins are cytoplasmic intermediate filament proteins expressed by epithelial cells. Cytokeratin MNF-116 is recommended for detection of keratin polypeptides of 45, 46 and 56.5 kDa. It is a broad spectrum cytokeratin marker which stains high and low molecular weight cytokeratins (CK 5, 6, 8, 17 and probably 19). Most epithelial cells, including lung type II epithelial cells, trophoblasts and uterine smooth muscle express cytokeratin MNF-116. In disease most carcinomas, mesothelioma and pituitary adenoma show positive staining.