Correlation of spectral imaging and visual grading for the quantification of thymidylate synthase protein expression in rectal cancer.

Quantification of protein expression in tissue sections stained by immunohistochemistry has traditionally involved visual grading techniques. However, if these results are to be used to predict tumor behavior and permit targeted therapy, there is a need for more accurate, objective, and reproducible methods. This study investigated the utility of spectral imaging as a method of quantifying thymidylate synthase protein expression in immunohistochemically stained sections of primary rectal cancer and normal rectal mucosa by comparing it with the current gold standard of manual visual grading. There was good correlation between estimates of thymidylate synthase stain intensity and area derived by spectral imaging and visual grading in both tumor and normal mucosal sections, suggesting that spectral imaging is a valid way of quantifying biologic sections stained by immunohistochemistry.