Pattern of mismatch repair proteins in colorectal cancer patients in tertiary cancer center.

Abstract

40 Background: Prevalence of MSI high in colorectal cancer patients in India has been debated in previous literature. Microsatellite instability pathway is one of the major pathways in carcinogenesis of colorectal carcinoma. MSI status has paramount significance in therapeutic and prognostic aspects of colorectal cancer management. MSI status can be evaluated by presence or absence of mismatch repair proteins. Aims & objectives: we aimed to determine the prevalence of MSI high in colorectal carcinoma and pattern of mismatch repair proteins. Methods: This was retrospective study which included consecutively operated colorectal carcinoma patients from 01 may 2022 to 31 December 2022 in our institute. Immunohistochemistry with four mismatch repair (MMR) proteins; MLH1, MSH2, MSH6, and PMS2 was performed. Correlation with various clinical and histopathological features was done. Results: total 296 colorectal carcinoma patients were included in our study. Fourty one (13.85%) patients were MSI high. Most common pattern of MMR protein expression loss was dual loss of MLH1 and PMS2 (n=18). Most common single protein loss was PMS2 (n=22). Most common location of tumor in MSI high patients was the right colon. (n=20). Out of 153 carcinoma rectum patients only five patients were MSI high. Conclusions: The study shows that prevalence of MSI high is more common in right colon cancer. Prevalence of MSI high is very low in carcinoma rectum. We discuss and compare our results with previous studies.