Three or more family members with a confirmed diagnosis of colorectal cancer, one of whom is a first degree (parent, child, sibling) relative of the other two
Two successive affected generations
One or more colon cancers diagnosed under age 50 years
Familial adenomatous polyposis (FAP) has been excludedThe Amsterdam II criteria were developed in 1999 and improved the diagnostic sensitivity for Lynch syndrome by including cancers of the endometrium, small bowel, ureter and renal pelvis.Amsterdam Criteria II (all bullet points must be fulfilled):

Three or more family members with HNPCC-related cancers, one of whom is a first-degree relative of the other two
Two successive affected generations
One or more of the HNPCC-related cancers diagnosed under age 50 years
Familial adenomatous polyposis (FAP) has been excludedThe Bethesda criteria were developed in 1997 and later updated in 2004 by the National Cancer Institute to identify persons requiring further testing for Lynch syndrome through MSI. In contrast to the Amsterdam Criteria, the Revised Bethesda Guidelines use pathological data in addition to clinical information to help health care providers identify persons at high risk.Revised Bethesda Guidelines
If a person meets any 1 of 5 criteria the tumour(s) from the person should be tested for 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%.