Table IV

Advantages and disadvantages of IHC and FISH-based testing for HER-2/neu in breast cancer

Advantages• Widely available• DNA is a stable target
• Rapid procedure• Standardized threshold for positivity
• Light microscope based• Built-in internal control
• Hercep Test™ and Pathway™ FDA-approved assays for Herceptin eligibility selection• Low interlaboratory variability
• High accuracy (sensitivity and specificity)
Disadvantages• Variable antibody sensitivity and specificity• Fluorescence microscope equipped with correct filter sets is required
• Highly impacted by tissue processing variables• Certain fixatives interfere with assay (noninformative result)
• Affected by antigen retrieval and reagent variability• Limited community experience with tissue-based FISH
• Non-FDA-approved assays in routine use
• Subjective scoring criteria
• Low pathologist concordance and high interlaboratory variability