This antibody is intended for in vitro diagnostic use. Ventana Medical Systems, Inc. (Ventana) anti-Pan Keratin (AE1/AE3/PCK26) Primary Antibody may be used to aid in the identification of normal and abnormal epithelial cells and to determine the lineage of poorly differentiated malignant tumors. The keratins are a group of intermediate filament proteins that occur in normal and neoplastic cells of epithelial origin. Nineteen human cytokeratins are known which are divided into acidic and basic subfamilies. They occur in pairs in epithelial tissues, the composition of pairs varying with the epithelial cell type, stage of differentiation, cellular growth environment, and disease state. This pan keratin cocktail recognizes most of the acidic and all of the basic cytokeratins, making it a useful stain for nearly all epithelial tissues and their tumors. Anti-Pan Keratin (AE1/AE3/PCK26) specifically binds to antigens located in the cytoplasm of simple and complex epithelial cells. The antibody is intended for laboratory use to qualitatively stain cytokeratins in sections of formalin fixed, paraffin embedded tissue on a Ventana automated slide stainer. Anti-Pan Keratin (AE1/AE3/PCK26) contains a mouse monoclonal antibody cocktail raised against an epitope found on human epidermal keratins as reported by Woodcock-Mitchell, et al.1 This antibody cocktail reacts with the 56.5kD, 50kD, 50’kD, 48kD, and 40kD cytokeratins of the acidic subfamily and 65-67kD, 64kD, 59kD, 58kD, 56kD, and 52kD cytokeratins of the basic subfamily.1,2,3,4,5 Unexpected antigen expression or loss of expression may occur, especially in neoplasms. Occasionally stromal elements surrounding heavily stained tissue and or cells will show immunoreactivity. The clinical interpretation of any staining, or the absence of staining, must be complemented by morphological studies and evaluation of proper controls. Evaluation must be made by a qualified pathologist within the context of the patient’s clinical history and other diagnostic tests. Caution: U.S. Federal law restricts this device to sale by or on the order of a physician.