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Hereditary colon cancers of the nonpolyposis type (HNPCC) or Lynch Syndrome (LS) is an inherited cancer syndrome caused by a germline mutation in one of several genes involved in DNA mismatch repair (MMR), including MLH1, MSH2, MSH6 and PMS2, or EPCAM gene. It is estimated to account for 1-3% of colorectal cancer (CRC). Although HNPCC is characterized by abnormal immunohistochemistry for MMR proteins and microsatellite instability (MSI-H), cancers exhibiting abnormal IHC for MLH1 and are MSI-H are most often sporadic (non-inherited) and due to abnormal methylation of the MLH1 gene promoter. Tumors that have the BRAF V600E mutation and MLH1 promoter hypermethylation are almost certainly sporadic, whereas tumors that show neither are most often caused by an inherited mutation. Testing for methylation of the MLH1 promoter can help distinguish sporadic from inherited cancers.