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 .MutS Homologue 2 (MSH2) is a Mismatch repair (MMR) protein. Its deficiency results in microsatellite instability (MSI). Defective MMR will show loss of expression of the protein. It is usually associated with loss of MSH6. Sequencing and/or large deletion/duplication testing of germline MSH2 may be indicated. People with MSH2 mutations have Lynch syndrome, previously known as hereditary non-polyposis colorectal cancer (HNPCC).