ABSTRACT
Cytokeratins (CK) are one of the five classes of intermediate filament proteins (IFP) and are found exclusively in cells displaying epithelial differentiation. Their most important diagnostic use, therefore, is in the positive identification of carcinomas, for which CK are a highly sensitive marker. A variety of different polyclonal and monoclonal antibodies that recognize CK are currently available commercially. If used correctly, these antibodies can be powerful ancillary tools for the surgical pathologist, as they are capable of distinguishing carcinomas from other poorly differentiated tumors, including lymphomas, sarcomas, melanomas, and primary central nervous system neoplasms. Furthermore, with the use of selected antibodies to CK proteins, one can begin to subclassify carcinomas according to their primary sites. In this chapter, the biology of CK, the antibodies that recognize these proteins, and their use in tumor diagnosis are reviewed.
