Assessment of prevalence of microsatellite instability by immunohistochemistry in colorectal cancer: experience from a tertiary cancer care centre in north east india

Objective: The aim of our study was to assess the prevalence of Microsatellite instability with the help of Immunohistochemistry in patients presenting with colorectal cancer and correlating MSI status with clinicopathological parameters.
Methods: Retrospective analysis of 61 cases of Colorectal cancer were analyzed who underwent surgery and histopathological examination in our hospital .All clinical information related to patient were retrieved, representative slides were retrieved and revaluation of histological parameters which are predictors of MSI phenotype was done. Representative blocks were selected and Immunohistochemistry for MLH1, MSH2, MSH6 PMS2 antibody were done to assess MSI status
Result: 61 cases of CRC the prevalence of MSI with the help of Immunohistochemistry was found to be 23% (14 cases were MSIH). MSIL was seen in 1.6% (1 case) and MSS in 75.4%(46 cases). MSIH tumours were found to be associated with proximal colon, MSI Histology (Mucinous Carcinoma/Signet ring cell carcinoma/Medullary Carcinoma), TIL Grade III, lymphnode negative status(pN0), low stage(Stage I and Stage II) and statistically significant correlation was found between the above parameters and MSIH.
Conclusion: In our study higher prevalence of MSIH was seen compared to Western literature, stressing the need for more widespread testing for better clinical management and identification of possible hereditary colon cancer syndrome.