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%.
Hereditary nonpolyposis colorectal cancer (HNPCC) or Lynch syndrome is an autosomal dominant genetic condition that is associated with a high risk of colon cancer as well as other cancers including endometrial cancer (second most common), ovary, stomach, small intestine, hepatobiliary tract, upper urinary tract, brain, and skin. The increased risk for these cancers is due to inherited mutations that impair DNA mismatch repair. It is a type of cancer syndrome. Because patients with Lynch syndrome can have polyps, the term HNPCC has fallen out of favor. Signs and symptoms
Risk of cancer
Lifetime risk and mean age at diagnosis for Lynch syndrome associated cancers

In addition to the types of cancer found in the chart above, it is understood that Lynch syndrome also contributes to an increased risk of small bowel cancer, pancreatic cancer, ureter/renal pelvis cancer, biliary tract cancer, brain cancer, and sebaceous neoplasms. Increased risk of prostate cancer and breast cancer has also been associated with Lynch syndrome, although this relationship is not entirely understood.Two-thirds of colon cancers occur in the proximal colon and common signs and symptoms include blood in the stool, diarrhea or constipation, and unintended weight loss. The mean age of colorectal cancer diagnosis is 44 for members of families that meet the Amsterdam criteria. The average age of diagnosis of endometrial cancer is about 46 years. Among women with HNPCC who have both colon and endometrial cancer, about half present first with endometrial cancer, making endometrial cancer the most common sentinel cancer in Lynch syndrome.