. Symptoms, initial diagnosis, and treatment are similar to other forms of colorectal cancer. Lynch syndrome is suspected by history and is confirmed by genetic testing. Patients also require surveillance for other cancers, particularly endometrial and ovarian cancer. Treatment is surgical resection.Lynch syndrome is an autosomal dominant disorder in which patients with one of several known genetic mutations that impair DNA mismatch repair have a 70 to 80% lifetime risk of developing colorectal cancer Colorectal Cancer Colorectal cancer is extremely common. Symptoms include blood in the stool and change in bowel habits. Screening using one of several methods is recommended for appropriate populations. Diagnosis... read more (CRC). Compared to sporadic forms of colon cancer, Lynch syndrome occurs at a younger age (mid 40s), and the lesion is more likely to be proximal to the splenic flexure. The precursor lesion is usually a single colonic adenoma, unlike the multiple adenomas present in patients with familial adenomatous polyposis Familial Adenomatous Polyposis Familial adenomatous polyposis is a hereditary disorder causing numerous colonic polyps and frequently resulting in colon carcinoma, often by age 40. Patients are usually asymptomatic but may... read more 
, the other main hereditary form of CRC.
However, similar to familial adenomatous polyposis, numerous extracolonic manifestations occur. Nonmalignant disorders include café-au-lait spots and sebaceous gland tumors. The low-grade skin cancer, keratoacanthoma Keratoacanthoma Keratoacanthomas are round, firm, usually flesh-colored nodules with sharply sloping borders and a characteristic central crater containing keratinous material; they usually resolve spontaneously... read more 
, can occur. Other common associated cancers include endometrial tumors Endometrial Cancer Endometrial cancer is usually endometrioid adenocarcinoma. Typically, it manifests as postmenopausal uterine bleeding. Diagnosis is by biopsy. Staging is surgical. Treatment requires hysterectomy... read more and ovarian tumors Ovarian, Fallopian Tube, and Peritoneal Cancer Ovarian cancer is often fatal because it is usually advanced when diagnosed. The most common histology—high-grade serous epithelial ovarian cancer—is considered as a single clinical entity along... read more (39% risk of endometrial and 9% risk of ovarian by age 70). Patients also have an elevated risk of other cancers, including of the stomach Stomach Cancer Etiology of stomach cancer is multifactorial, but Helicobacter pylori plays a significant role. Symptoms include early satiety, obstruction, and bleeding but tend to occur late in the... read more 
, urinary tract, pancreas Pancreatic Cancer Pancreatic cancer, primarily ductal adenocarcinoma, accounts for an estimated 57,600 cases and 47,050 deaths in the US annually ( 1). Symptoms include weight loss, abdominal pain, and jaundice... read more , biliary tree, gallbladder, small bowel Small-Bowel Tumors Small-bowel tumors account for 1 to 5% of gastrointestinal tumors. Small-bowel cancer accounts for an estimated 11,110 cases and about 1,700 deaths in the US annually ( 1). Diagnosis is by enteroclysis... read more , and brain Overview of Intracranial Tumors Intracranial tumors may involve the brain or other structures (eg, cranial nerves, meninges). The tumors usually develop during early or middle adulthood but may develop at any age; they are... read more 
.
Symptoms and Signs of Lynch Syndrome
Symptoms and signs of Lynch syndrome are similar to other forms of colorectal cancer, and diagnosis and management of the tumor itself are the same.
Diagnosis of Lynch Syndrome
Detailed family history
Clinical criteria followed by testing for microsatellite instability (MSI) or with immunohistochemistry (IHC)
Genetic testing for confirmation
(See also the 2015 American Gastroenterological Association's guideline regarding diagnosis and management of Lynch syndrome and the American College of Gastroenterology's clinical guideline on the genetic testing and management of hereditary gastrointestinal cancer syndromes.)
The specific diagnosis of Lynch syndrome is confirmed by genetic testing. However, deciding who to test is difficult because, unlike familial adenomatous polyposis, there is no typical phenotypic appearance. Thus, suspicion of Lynch syndrome requires a detailed family history, which should be obtained in all younger patients identified with colorectal cancer (CRC).
To meet the Amsterdam II criteria for Lynch syndrome, all three of the following historical elements must be present:
Three or more relatives with CRC or a Lynch syndrome–associated cancer
CRC involving at least two generations
At least one case of CRC before age 50
Other prediction models (eg, the PREMM5 model) and other criteria (eg, the Bethesda criteria [ 1 Diagnosis reference Lynch syndrome is an autosomal dominant disorder responsible for 2 to 3% of cases of colorectal cancer. Symptoms, initial diagnosis, and treatment are similar to other forms of colorectal cancer... read more ]) are used by some health care practitioners.
Patients meeting these criteria should have their tumor tissue tested either for MSI or with IHC to detect proteins responsible for DNA mismatch repair; however, most commercial and hospital pathology laboratories now routinely do this test on all colorectal adenocarcinoma specimens. The 2015 American Gastroenterological Association guidelines recommend that tumors of all patients with CRC should be tested either with IHC or for MSI. If MSI or IHC is positive, genetic testing for specific Lynch syndrome mutations is indicated.
Patients with Lynch syndrome should have a surveillance colonoscopy every 1 to 2 years. Patients with confirmed Lynch syndrome require ongoing screening for other cancers. For endometrial cancer, annual endometrial aspiration or transvaginal ultrasound is recommended. For ovarian cancer, options include annual transvaginal ultrasound and serum CA 125 levels. Prophylactic hysterectomy and oophorectomy are also options. Urinalysis may be used to screen for renal tumors.
First-degree relatives of patients with Lynch syndrome should have genetic testing. If no genetic testing has been done, they should have colonoscopy every 1 to 2 years beginning in their 20s, and annually after age 40. Female 1st-degree relatives should be tested annually for endometrial and ovarian cancer.
Diagnosis reference
1. Umar A, Boland CR, Terdiman JP, et al: Revised Bethesda guidelines for hereditary nonpolyposis colorectal cancer (Lynch syndrome) and microsatellite instability. J Natl Cancer Inst 96(4):261–268, 2004. doi: 10.1093/jnci/djh034
Treatment of Lynch Syndrome
Surgical resection
The most common treatment of Lynch syndrome is resection of the index lesion with frequent surveillance for another colon cancer and any associated tumors in other organs. Because most Lynch syndrome tumors occur proximal to the splenic flexure, subtotal colectomy, leaving the rectosigmoid intact, has been suggested as an alternative. In either case, close follow-up is needed.
Key Points
Certain autosomal dominant mutations confer a 70 to 80% lifetime risk of developing colorectal cancer.
Patients also have an increased risk of other cancers, particularly of the endometrium and ovary.
Symptoms, initial diagnosis, and treatment are similar to other forms of colorectal cancer.
Patients with certain familial risk factors should have their tumor tissue tested for microsatellite instability or with immunohistochemistry; if positive, genetic testing is done.
First-degree relatives who have not undergone genetic testing should have colonoscopy every 1 to 2 years beginning in their 20s, and annually after age 40; women should also be tested annually for endometrial and ovarian cancer.
More Information
The following are some English-language resources that may be useful. Please note that THE MANUAL is not responsible for the content of these resources.
PREMM5: Prediction model for MLH1, MSH2, MSH6, PMS2, and EPCAM gene mutations
