MSI-High Colorectal CA : Introduction
About 15% of colorectal carcinomas (CRCs), including Hereditary Non-polyposis Colorectal Cancer (HNPCC; Lynch Syndrome), right-sided sporadic CRC, and serrated adenocarcinomas show defective DNA mismatch repair (MMR) pathway leading to microsatellite instability (MSI). These tumors show hypermutations, are more likely to be poorly-differentiated with little or no gland formation or show mucinous differentiation. Growth pattern is often circumscribed. Tumor infiltrating lymphocytes are consistently present.