Two tests evaluating the same tumor can sometimes produce different results—and both may still be correct.
In a new Precision Medicine article from the College of American Pathologists, the co-authors Matthew Hiemenz, MD, FCAP and Jeremy Ward, MD, PhD, FCAP, explain why commonly used methods for assessing mismatch repair and microsatellite instability, such as immunohistochemistry (IHC), PCR, and next-generation sequencing, can produce discordant findings.
The reason: these tests measure different aspects of tumor biology. IHC evaluates protein expression, while molecular assays assess DNA-level instability. Because of this, each method can identify cases the others may miss.
Rather than signaling an error, discordant results can reflect the underlying complexity of cancer. Experts say the future of precision oncology lies in integrating multiple testing approaches to better guide immunotherapy decisions.