TY - CHAP M1 - Book, Section TI - Colorectal Cancer, Hereditary Nonpolyposis (HNPCC) A1 - Doherty, Gerard M. PY - 2010 T2 - Quick Answers Surgery AB - • Perhaps 6% of patients with cancer of the colon or rectum have HNPCC• Most common form of hereditary colorectal cancer• Gene responsible for this syndrome has been localized to chromosome 2p• Lynch syndrome II:-Early onset (average age 44)-Proximal dominance-Synchronous and metachronous cancers and other associated extracolonic adenocarcinomas, especially endometrial carcinoma• Lynch syndrome I: Hereditary site-specific colon cancer shows the same characteristics except that there are no extracolonic cancers• Autosomal dominant inheritance• Cancers arise in discrete adenomas but polyposis (ie, hundreds of polyps) does not occur• Diagnostic criteria (Amsterdam criteria)-Families must have at least 3 relatives with colorectal cancer, 1 of whom is a first-degree relative of the other 2-Colorectal cancer must involve at least 2 generations, and at least 1 cancer case must occur before age of 50• Adenomas and carcinomas in HNPCC arise at an early age-Adenomas may occur in patients in their 20s and 30s, with a mean age for carcinoma development of 40 to 45 years-Are often proximal in location and multiple• Alterations in DNA mismatch repair genes that help maintain DNA fidelity during replication are characteristic of patients with HNPCC: (hMLH1, hPMS1 and hPMS2, and hMSH2, hMSH3, and hMSH6) may lead to the inability to repair base pair mismatches and result in DNA replication errors or microsatellite instability• Accelerated carcinogenesis occurs in hereditary nonpolyposiscolorectal cancer compared with sporadic cases SN - PB - The McGraw-Hill Companies CY - New York, NY Y2 - 2024/03/28 UR - accesssurgery.mhmedical.com/content.aspx?aid=58108040 ER -