Test Details: Immunohistochemical 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). 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)