Specificity: Reacts with cytokeratin 10 and 13 in fixed cells and on frozen tissues, but exclusively with cytokeratin 13 in formalin-fixed, paraffin-embedded tissues. Cytokeratin 10 is present in keratinizing stratified epithelia and in differentiated areas of highly differentiated squamous cell carcinomas, while cytokeratin 13 is present in non-cornified squamous epithelia, except cornea, and transitional epithelial regions, with the exception of basal cell layers of some stratified epithelia, as well as carcinomas derived from these tissues.