msi: 1. colorectal cancer diagnosed before age 50 2. presence of synchronous or metachronous colorectal or other lynch syndrome associated cancers (e.g. cancers of endometrium, ovary, stomach, small bowel, pancreas, biliary tract, ureter, renal pelvis, brain, sebaceous glands, keratoacanthomas) 3. colorectal cancer with msi-high pathology in a person who is younger than 60 years of age 4. colorectal cancer diagnosed in a person with one or more first-degree relative with colorectal cancer or lynch syndrome associated tumour diagnosed under age 50 5. person with colorectal cancer and two or more first- or second-degree relatives with colorectal cancer or lynch syndrome associated cancer diagnosed at any age. it is important to note that these clinical criteria can be difficult to use in practice and clinical criteria used alone misses between 12 and 68 percent of lynch syndrome cases. surgery prophylactic hysterectomy and salpingo-oophorectomy (removal of the uterus, fallopian tubes, and ovaries to prevent cancer from developing) can be performed before ovarian or endometrial cancer develops. treatment surgery remains the front-line therapy for hnpcc. patients with lynch syndrome who develop colorectal cancer may be treated with either a partial colectomy or total colectomy with ileorectal anastomosis. due to increased risk of colorectal cancer following partial colectomy and similar quality of life after both surgeries, a total colectomy may be a preferred treatment for hnpcc, especially in younger patients. there is an ongoing controversy over the benefit of 5-fluorouracil-based adjuvant therapies for hnpcc-related colorectal tumours, particularly those in stages i and ii. anti-pd-1 antibody therapy can be effective. checkpoint blockade with anti-pd-1 therapy is now preferred first line therapy for advanced microsatellite-instability–high colorectal cancer. epidemiology though the exact prevalence of lynch syndrome-causing mutations in the general population remain unknown, recent studies estimate the prevalence to be 1 in 279 individuals, or 0.35%. certain populations are known to have a higher prevalence of founder mutations, including, but not limited to, french canadians, icelanders, african americans, and ashkenazi jews. lynch syndrome-causing mutations are found in approximately 3% of all diagnosed colorectal cancers, and 1.8% of all diagnosed endometrial cancers. the average age of diagnosis of cancer in patients with this syndrome is 44 years old, as compared to 64 years old in people without the syndrome. terminology henry t. lynch, professor of medicine at creighton university medical center, characterized the syndrome in 1966. in his earlier work, he described the disease entity as "cancer family syndrome." the term "lynch syndrome" was coined in 1984 by other authors; lynch named the condition hnpcc in 1985. since then the two terms have been used interchangeably, until later advances in the understanding of the genetics of the disease led to the term hnpcc falling out of favor. other sources reserve the term "lynch syndrome" when there is a known dna mismatch repair defect, and use the term "familial colorectal cancer type x" when the amsterdam criteria are met but there is no known dna mismatch repair defect. the putative "type x" families appear to have a lower overall incidence of cancer and lower risk for non-colorectal cancers than families with documented dna mismatch repair deficiency. about 35% of people who meet amsterdam criteria do not have a dna-mismatch-repair gene mutation. complicating matters is the presence of an alternative set of criteria, known as the "bethesda guidelines." society there are a number of non-profit organisations providing information and support, including lynch syndrome international, aliveandkickn, lynch syndrome uk and bowel cancer uk. in the us, national lynch syndrome awareness day is march 22.