Detecting Lynch syndrome by pathologists.

Lynch syndrome (formerly called hereditary nonpolyposis colorectal cancer) is a hereditary syndrome resulting in a high risk for colorectal cancer at young age. About 2-3% of all colorectal cancers arise in the setting of Lynch syndrome and the tumors are characterized by microsatellite instabillity (MSI)due to a mutation in one of the mismatch repair genes. Of sporadic colorectal cancer about 15 % have MSI too, but due to hypermethylation of the promotor of the MHL1 gene. Recognizing Lynch syndrome is important, since patients and their families need to undergo a screening program. Based on clinical (colorectal cancer in patients younger than 50 years, or multiple colorectal cancer in one patient) and pathological (mucinous carcinoma, intraepithelial lymphocytes) features pathologists are increasingly able to recognize cases of colorectal cancer that are associated with Lynch syndrome. We propose a cost-effective and ethically correct approach for detecting Lynch syndrome by pathologists.