Fixation and epitope retrieval in diagnostic immunohistochemistry: a concise review with practical considerations

Diagnostic immunohistochemistry (DIHC) is an extremely valuable technological development that has revolutionized the practice of surgical pathology over the past 25 years. Like any laboratory procedure, however, the precise concatenation of methodological details that are used by any given investigator has a major effect on final results. In this overview, the authors consider several of these variables and illustrate how they may be optimized in an effective and efficient approach to quality assurance in the DIHC laboratory. The great majority of this discussion concerns processing factors as they affect paraffin section-based immunohistology because that is still, by far, the most common adjunctive morphologic procedure (AMP) used in hospital pathology. However, information is also presented on elements of tissue processing that affect other analyses as well. The material presented here is a direct reflection of the conjoint experiences of the authors. Although we discuss our preferences regarding many technical aspects of this discipline, we certainly do not mean to imply that ours are the only methods that should be utilized. Nevertheless, it is hoped that they may serve to crystallize basic concepts surrounding fixation, processing, and optimal performance of AMPs.