Immunohistology—Past, Present, and Future

Abstract

The rapid development of immunohistochemistry, a morphology-based technique, has come about through refinements in detection systems and an increasing range of sensitive and specific antibodies that have allowed application of the technique to formalin-fixed, paraffin-embedded tissues. The introduction of heat-induced antigen retrieval has been a significant milestone to compliment these developments so that the immunohistochemistry is firmly entrenched as an indispensable adjunct to morphologic diagnosis. Although this ancillary stain was initially used in a qualitative manner, problems surrounding the many variables that influence antigen preservation in formalin-fixed, paraffin-embedded tissues were not a major issue and laboratories strived to optimize their staining protocols to the material they accessioned and processed. The advent of personalized medicine and targeted cancer treatment has imposed the need to quantitate the stain reaction product and has resulted in calls to standardize the process of immunostaining. A closer examination of the variables that influence the ability to show antigens in formalin-fixed, paraffin-embedded tissues revealed many important variables, particularly in the preanalytical phase of the assay, that are beyond the control of the accessioning laboratory. Although analytical factors have the potential to be standardized, the actions of many pivotal procedures including fixation and antigen retrieval are not completely understood. Postanalytical processes including threshold and cut-off values require consensus and standardization and it is clear that some of these goals can be achieved through the direction of national and international organizations associated with cancer diagnosis and treatment. With the ability to serve as a surrogate marker of many genetic abnormalities, immunohistochemistry enters a new era and the need to better understand some of the mechanisms fundamental to the technique become more pressing and the development of true quantitative assays is imperative. There is also an increasing appreciation that the technique highlights patterns of staining that reflect exquisite localization to organelles and tissue structures that are not appreciable in routine stains, adding a further dimension to morphologic diagnosis.

The Use of Immunohistochemistry for Biomarker Assessment—Can It Compete with Other Technologies?

“…To this end, attempts have been made to standardize IHC assays upon which treatment decisions rest. However, to date, these approaches have failed to produce an overall system of IHC standards that ensure uniform high quality, with a level of reproducibility and reliability sufficient to allow robust comparison of IHC results across laboratories and platforms (T. Leong, Cooper, and Leong 2010;A. Leong and Leong 2011;Shi, Liu, and Taylor 2007;Taylor 2009).…”

A 92-gene cancer classifier predicts the site of origin for neuroendocrine tumors

“…Protein IHC has additional variation in antibody retrieval methods and antibody clone differences, as well as wide variation in techniques and controls used between labs; all these factors can all affect the rate of false positive and false negative IHC results. [68][69][70][71][72][73][74] In addition, selection of specific IHC markers and the interpretation of the protein expression patterns can be subjective and is dependent on the individual pathologist.…”

Multisite Validation Study to Determine Performance Characteristics of a 92-Gene Molecular Cancer Classifier

“…For distinguishing primary from metastatic carcinoma, no single immunohistochemical marker offers comparable performance. While immunohistochemical panels may improve performance, individual immunohistochemical markers are limited by lack of specificity, variable expression in poorly differentiated tumors, many technical sources of staining variance, and a subjective analytic approach and interpretation (46)(47)(48)(49)(50)(51)(52). Thus, the 92-gene assay may provide an important diagnostic adjunct, particularly in tumors with equivocal histopathology and immunohistochemistry, lack of specific clinical findings, and/or a range of differential diagnoses.…”