Test Details: Immunohistochemical testing is carried out on biopsy/resected tissue specimen. This testing helps to identify specific antigens (proteins) within tissue sections utilizing an antigen-specific antibody. Microsatellite instability (MSI) is caused by mutations in DNA mismatch repair genes such as MLH1, MSH2, MSH6, and PMS2, and it is found in 10% to 15% of sporadic colorectal cancers (CRCs). The presence of MSI predicts a good outcome in colorectal cancer. However, loss of these genes indicate that the person has high probability of Lynch syndrome previously known as hereditary non-polyposis colorectal cancer (HNPCC).