Identification and classification of hereditary nonpolyposis colorectal cancer (Lynch syndrome): adapting old concepts to recent advancements. Report from the Italian Association for the study of Hereditary Colorectal Tumors Consensus Group.

Knowledge about hereditary nonpolyposis colorectal cancer (HNPCC)/Lynch syndrome clearly evolved during the last 10 to 15 years much more rapidly than in the past century. Consequently, long-established concepts and attitudes that held for many years should now be changed or updated. With regard to classification, we suggest maintaining the eponym "Lynch syndrome" for families that have a well-documented deficiency of the DNA mismatch repair system, whereas "clinical hereditary nonpolyposis colorectal cancer" should be reserved for those families that meet the Amsterdam criteria but without evidence of mismatch repair impairment. Any family (or individual) meeting one or more of the Bethesda criteria can be considered as suspected HNPCC. For the identification of hereditary colorectal cancer molecular screening or the pedigree analysis show advantages and disadvantages; the ideal would be to combine the two approaches. Diffusion of the microsatellite instability test and of immunohistochemistry in the pathology laboratories might render in the immediate future molecular screening more realistic. Strict endoscopic surveillance of family members at risk (with first colonoscopy at age 20-25 years and then every 2-3 years) is needed only in families with documented alterations of the DNA mismatch repair. To a certain extent, our conclusions were similar to the recently proposed "European guidelines for the clinical management of HNPCC," although we prefer the term "clinical hereditary nonpolyposis colorectal cancer," instead of familial colorectal cancer, for families meeting the Amsterdam criteria but not having evidence of mismatch repair impairment.