Mis-Match Repair (MMR) Protein Expression and Microsatellite Instability (MSI) Analysis in Sporadic Adenocarcinoma Diagnosed on Colonoscopic Biopsy

Background and aim Colorectal adenocarcinoma is a major cause of morbidity and mortality worldwide. Mismatch repair MMR protein expression plays a crucial role in the development and progression of colorectal adenocarcinomas. Immunohistochemistry IHC is a widely used technique to assess MMR protein expression. However there is limited data on the prospective evaluation of MMR protein expression by IHC on endoscopic biopsies of colorectal adenocarcinomas. In this study we aimed to evaluate the MMR protein expression by IHC on endoscopic biopsies of colorectal adenocarcinomas at a tertiary care center.Methods Forty-Two colonoscopic endoscopic biopsies pathologically diagnosed as colorectal adenocarcinoma were analyzed for IHC expression of MMR proteins MLH1 PMS2 MSH2 and MSH6.Results Out of the 42 cases 22 52.3 were mismatch repair proficient pMMR while the remaining 20 47.6 were mismatch repair deficient dMMR. MLH1PMS2- was the most common pattern accounting for 20 of dMMR cases and MLH1-PMS2-MSH2-MSH6- or the ldquoNull Patternrdquo was the least common with 10 of dMMR cases.Conclusion Evaluation of MMR proteins using immunohistochemistry is relatively easy in routine testing and is a useful tool in detecting MSI in CRC.nbspnbsp