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Overview

What Is Lynch Syndrome?

Lynch syndrome is an inherited condition that increases a person’s risk of developing colorectal and several other cancers. It results from changes in DNA mismatch-repair genes, which normally help correct mistakes in DNA. A person can have Lynch syndrome without having cancer. It is also called hereditary nonpolyposis colorectal cancer, or HNPCC.

How It's Diagnosed

How Lynch Syndrome Is Diagnosed

Lynch syndrome may be suspected because of a personal or family history of related cancers, abnormal tumor testing, or both. The syndrome itself usually causes no symptoms, so some people are identified through cancer evaluation or family risk assessment. Lynch syndrome genetic testing is best planned and explained with professional genetic counseling.

  • Personal and family cancer history review helps identify patterns that may suggest inherited risk.
  • Genetic counseling explains possible results, benefits, limitations, and effects on relatives.
  • Tumor testing can examine available cancer tissue for signs of mismatch-repair problems.
  • Inherited gene testing uses a blood or saliva sample to look for a germline change linked to Lynch syndrome.

Causes

What Causes Lynch Syndrome?

Lynch syndrome is caused by an inherited pathogenic variant in a DNA mismatch-repair gene. When mismatch repair does not work properly, genetic damage can accumulate over time, increasing the chance that cells become cancerous. These variants usually follow an autosomal dominant inheritance pattern, meaning a person with the condition may pass the altered gene to a biological child.

INHERITED VARIANT

An inherited change is present in nearly every cell of the body and may be passed to biological children.

ACQUIRED TUMOR CHANGE

An acquired change develops in tumor cells and usually does not indicate inherited Lynch syndrome or a risk to biological children.

Risk Factors

Lynch Syndrome Risk Factors

  • A known Lynch syndrome gene variant in the family increases the likelihood of inherited risk.
  • A first-degree relative with Lynch syndrome may indicate that genetic counseling is appropriate.
  • Colorectal or endometrial cancer diagnosed at a younger-than-usual age can be a warning sign.
  • More than one Lynch-associated cancer in the same person may suggest an inherited cancer syndrome.
  • Several related cancers across generations can point to a familial Lynch syndrome pattern.

Lynch syndrome is primarily genetic and is not caused by a person’s diet, stress, or another modifiable behavior. Lifestyle factors can still influence overall cancer risk, but changing them does not remove an inherited Lynch syndrome gene variant. A genetic counselor can help interpret family history and determine whether testing is appropriate.

Complications

Complications and Cancer Risks

  • Colorectal cancer is a major cancer risk associated with Lynch syndrome.
  • Endometrial cancer risk is increased, particularly for people with a uterus.
  • Ovarian cancer risk may also be increased.
  • Stomach and small-intestine cancers are among the less common associated risks.
  • Urinary-tract cancers, including cancers of the ureter or renal pelvis, can occur.
  • Pancreatic and biliary-tract cancers have been associated with Lynch syndrome.
  • Selected brain and skin cancers may occur in some people with Lynch syndrome.

The exact Lynch syndrome cancer profile depends partly on the affected gene, along with personal and family history. People with Lynch syndrome can develop more than one primary cancer during their lifetime, so care often includes ongoing surveillance for more than one cancer type.

Important

Do not ignore new symptoms

New, persistent, or unusual symptoms should be assessed promptly, even when you are following a planned surveillance schedule. Screening lowers risk from delayed detection but does not rule out cancer between scheduled visits.

Treatment & Management

Treatment and Management of Lynch Syndrome

SURVEILLANCE

Earlier and more frequent screening is used to find cancers promptly, especially colorectal and endometrial cancers.

RISK REDUCTION

Medicines or preventive surgery may be discussed with a specialist when the expected benefit outweighs the risks.

CANCER TREATMENT

Any diagnosed cancer is treated according to its site, stage, tumor features, and the person’s overall health.

Management should be individualized according to the affected gene, age, sex, previous cancers, and reproductive plans. Genetic counseling helps coordinate care, document family history, discuss reproductive considerations, and help relatives decide whether testing is appropriate. A hereditary cancer team can update the plan as guidelines and a person’s health change.

Prevention & Screening

Prevention and Screening for Lynch Syndrome

  • Earlier and more frequent colonoscopy should follow the schedule recommended by a clinician familiar with the affected gene.
  • Abnormal uterine bleeding or other gynecologic symptoms should be evaluated promptly.
  • Upper gastrointestinal or urinary-tract screening may be considered when the gene, family history, or guidelines indicate it.
  • Risk-reducing gynecologic surgery can be discussed with appropriate patients after considering health and reproductive plans.
  • Genetic counseling and cascade testing can help eligible relatives learn whether they share the familial variant.

Outlook and Prognosis

Outlook and Prognosis

Lynch syndrome is a lifelong inherited cancer risk rather than a cancer that can be cured. Regular surveillance can help detect Lynch syndrome cancers earlier and may reduce complications that could otherwise be prevented through timely care. Ongoing follow-up is important even when a person feels well.

Next Steps After Diagnosis

Next Steps After a Lynch Syndrome Diagnosis