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 1 (MLH1) is a Mismatch repair (MMR) protein. Its deficiency results in microsatellite instability (MSI). PMS2 expression is almost always lost as well along with MLH1. In case of loss of nuclear expression of both MLH1 and PMS2: testing for methylation of the MLH1 promoter and/or mutation of BRAF is indicated. The presence of a BRAF V600E mutation and/or MLH1 methylation suggests that the tumour is sporadic and germline evaluation is probably not indicated; absence of both MLH1 methylation and of BRAF V600E mutation suggests the possibility of Lynch syndrome ( also known as hereditary non-polyposis colorectal cancer (HNPCC), is the most common cause of hereditary colorectal (colon) cancer.).