Test Details: Immunohistochemical 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. Loss of nuclear expression of MSH2 indicates high probability of Lynch syndrome (sequencing and/or large deletion/duplication testing of germline MSH2 may be indicated).