Lynch Syndrome Genetic Testing: Who Should Be Tested and How It Works

Lynch syndrome genetic testing is a germline test, usually run on blood, that looks for inherited changes in MLH1, MSH2, MSH6 and PMS2 and for deletions at the end of neighboring EPCAM. GeneReviews says the diagnosis is established when a pathogenic variant is found in one of them. ^[1]

A germline test examines DNA present throughout the body and asks what can be inherited. A tumor test examines cancer tissue for mismatch-repair protein loss or microsatellite instability; it is a screen that can point toward germline testing, not the same test. See tumor testing (MSI and IHC). ^[1,2]

Blood is usual, while some laboratories accept saliva or a cheek swab. GeneReviews estimates Lynch syndrome affects about 1 in 280–600 people; Win and colleagues estimated about 1 in 279 in a population analysis. These differences explain why rounded figures such as “about 1 in 300” also appear. For condition background, read what Lynch syndrome is. ^[1,4,13]

The CDC says testing is usually recommended after an abnormal tumor test, colorectal cancer, endometrial cancer before age 50, several cancers, several relatives with Lynch-related cancers, or a relative with Lynch syndrome. A genetic counselor or doctor decides which criteria apply. ^[2]

Sources differ on the endometrial age cutoff; a genetic counselor applies current NCCN criteria. Most cancers are not caused by Lynch syndrome, and a family history does not itself establish Lynch syndrome. When there is no personal or family history of Lynch-related cancers, the CDC says testing is unlikely to help. Predictive testing is generally an adult decision; children need specialist review rather than a one-size-fits-all age rule. ^[1,2,3]

A history dominated by breast, ovarian or prostate cancer may raise a different inherited-risk question; see BRCA1 and BRCA2 testing.

Testing usually starts with a genetic counselor reviewing personal and family history, then a blood sample goes to a laboratory for a multigene panel. When possible, the CDC recommends starting with a relative who has had cancer. If a family variant is known, relatives can be tested for that variant. ^[2,4]

At $599 one time, people may also consider HLI’s at-home saliva clinical whole-genome sequencing, processed in a CLIA-certified laboratory, for a broader view of inherited risk; it is not diagnostic or a replacement for tumor testing or a clinic-ordered Lynch panel, and HLI’s Lynch-gene coverage, deletion/duplication support and PMS2 handling remain unconfirmed.

1. 01

   Screen a tumor when cancer is present

   Colorectal or endometrial cancers are commonly screened by tumor testing (MSI and IHC). An abnormal screen can lead to germline testing.

2. 02

   Review history before testing

   A genetic counselor documents cancers, ages and both sides of the family. Clinicians may use PREMM5, MMRpro or MMRpredict as decision aids.

3. 03

   Collect a sample

   Blood is common; saliva or cheek-swab DNA may be accepted. After an allogeneic bone-marrow transplant, donor DNA can interfere with blood testing, so the laboratory needs advance notice and specialized specimen planning. ^[14]

4. 04

   Choose panel or single-site testing

   A multigene panel is typical when the cause is unknown. When a familial variant is known, testing that specific change is usually the direct route.

5. 05

   Interpret the result with counseling

   The laboratory classifies findings, but personal and family history determine what a positive, negative or uncertain result means.

A complete Lynch syndrome test covers MLH1, MSH2, MSH6 and PMS2 plus EPCAM 3′ deletions. GeneReviews reports that deletions and duplications make up a substantial share of findings in some genes, so sequence analysis alone is not enough. ^[1]

Source: GeneReviews Table 1, updated September 17, 2026. EPCAM sequence analysis without deletion analysis is not an appropriate Lynch test. Panel gene lists vary by laboratory. ^[1]

A positive result means a pathogenic variant was found and Lynch syndrome is diagnosed. A negative result can be a true negative or an uninformative negative. A variant of uncertain significance neither establishes nor rules out Lynch syndrome, and relatives should not be tested for it as though it were causal. ^[1,2]

A true negative means the change known to run in the family was not found; the CDC says that person is not at increased risk from that family variant and their children do not need testing for it. An uninformative negative cannot erase a strong history. Review every result with a genetic counselor, and ask the laboratory periodically—often annually—whether a VUS has been reclassified. ^[2]

In the United States, GINA protects against genetic discrimination in health insurance and employment, but not life, disability or long-term-care insurance. ^[15]

The Amsterdam criteria, called the 3-2-1 or 3/2:1 rule, flag families with at least three relatives with a Lynch-related cancer, in two successive generations, with at least one diagnosis before 50. The revised Bethesda guidelines identify colorectal tumors for microsatellite-instability testing. Neither is a self-diagnosis. ^[6,7]

These are historical triage tools, not modern stand-alone diagnostic criteria. Strafford reported that about 35% of families meeting Amsterdam criteria had no mismatch-repair variant and about 50% of families with Lynch syndrome failed Amsterdam criteria. The American Cancer Society likewise notes that most people meeting Bethesda guidelines do not have Lynch syndrome and that Lynch syndrome can occur without meeting them. ^[8,12]

Current practice favors universal mismatch-repair screening of colorectal and endometrial cancers, supported by NCCN, ACG guidance and NICE DG27/DG42, alongside clinical risk models. Some summaries paraphrase Bethesda differently; the five-item list here follows the 2004 publication. See the modern tumor-testing pathway. ^{[3,5,7,10,11]}

A blood sample is the usual specimen for Lynch syndrome testing, but the laboratory must analyze MLH1, MSH2, MSH6, PMS2 and EPCAM with appropriate deletion and duplication methods. Mayo Clinic says there are no reliable at-home kits for Lynch syndrome because limited-marker kits do not provide the detailed testing these genes require. ^[1,4]

Genotyping chips compare DNA at a fixed list of preselected positions. Sequencing reads through a gene or broader region, while separate copy-number methods may be needed for deletions and duplications. Whether a consumer sequence covers all relevant genes, EPCAM deletions and copy-number changes depends on its published report scope.

Coverage depends on the insurer, plan and whether the person meets its medical-necessity criteria. No verified payer policy or primary laboratory price list was supplied for this page, so a coverage promise or clinical-panel price would be unsupported. Confirm authorization and personal cost before testing.

Ask the ordering clinic and insurer about eligibility criteria, prior authorization, network status, genetic-counseling benefits and the laboratory’s self-pay policy. GINA protects health insurance and employment in defined circumstances, but does not cover life, disability or long-term-care insurance. ^[15]

HLI lists its whole-genome service at $599 as a one-time price. That is not a quote for a clinical Lynch syndrome panel.

After a positive result, care usually means earlier and more frequent gene-specific screening plus testing relatives for the same variant. Mayo Clinic describes colonoscopy beginning at ages 20–25, or two to five years before the youngest family diagnosis, repeated every one to two years; individual guidance can differ. ^[4]

Parents, siblings and children are first-degree relatives. When a family variant is known, they are tested for that variant rather than starting with an unrestricted search. Each child has a 50% chance of inheriting it. A genetic counselor can help explain which adult relatives to contact and what a true negative means. ^[1]

For management details, read about colonoscopy and surveillance after a result. Women can also review endometrial and ovarian cancer risk. Treatment decisions are outside this testing guide.