Subjective differences in outcome are seen as a function of the immunohistochemical method used on a colorectal cancer tissue microarray.

Immunohistochemistry is a useful technique to localize antigens in cell preparations and tissue sections and can be helpful in identifying molecular markers that may be predictive of patient outcomes. Subjective assessment of expression and semiquantitative grading systems are the current standards in pathology literature for the analysis of tissue sections. However, expression levels assessed in this manner may be dramatically affected by the method of visualization. Tissue microarray (TMA) is a recently developed technique for the simultaneous high-throughput evaluation of protein expression on tissue samples from large cohorts of patients. The scoring of TMAs has, in general, mirrored the systems utilized for tissue sections. Here, 4 detection systems (avidin-biotin complex, indirect immunofluorescence, peroxidase-labeled polymer conjugate, and the latter with Cyanine-3-Tyramide amplification) were compared using a beta-catenin antibody on a TMA containing a cohort of colorectal cancer specimens. Peroxidase-labeled polymer with or without tyramide enhancement was found to be the most sensitive method, revealing a greater staining intensity and percentage of nuclear staining, without an apparent increase in background. Subjective assessment of expression is highly dependent on the method of visualization and may illustrate why discrepant data is often seen in literature based on immunohistochemistry.