Assessment of microsatellite instability in colorectal carcinoma at an Indian center

Abstract

The purpose of the present study was to evaluate the frequency of microsatellite instability (MSI) in colorectal cancers in an Indian cohort. Paraffin embedded tissue samples of colorectal cancers from 46 patients were assessed for mismatch repair protein expression (hMLH1 and hMSH2) by immunohistochemistry. Subsequently, MSI analysis was done after PCR amplification of five Bethesda markers. Amongst 46 cases studied, only 5 patients (10.8%) showed MSI. Out of these, two (4.3%) had high microsatellite instability (MSI-H) and three (6.5%) showed low microsatellite instability (MSI-L). Out of 46 cases, 41 were microsatellite stable (MSS). In the 46 cases tested by immunohistochemistry, 7 (15.7%) showed the absence of hMLH1 and 1 case showed the absence of hMSH2. Our study indicates a similar rate of incidence of MSI in colorectal cancers in the Indian cohort compared to the West (10-15%) despite lower incidence of colorectal cancers and predominance of rectosigmoid tumors in the Indian population.