Lynch Syndrome: Inherited Colorectal and Other Cancer Risk

The simple versionExplain▾

Lynch syndrome is an inherited condition. It is caused by changes in genes that normally help your cells repair DNA. When those genes do not work well, errors can build up and raise the risk of certain cancers.

Lynch syndrome most often raises the risk of colorectal cancer (colon and rectum) and endometrial cancer (the lining of the uterus). It can raise the risk of some other cancers too, and related cancers often appear at younger ages than usual.

Lynch syndrome raises cancer risk — but knowing about it opens the door to screening that can catch or even prevent cancer.

How Lynch syndrome worksExplain▾

Your cells have a repair system that fixes small mistakes when DNA is copied, sometimes called mismatch repair. Lynch syndrome involves inherited changes in the genes that run this system.

When these genes do not work properly, mistakes in the DNA can pile up faster. Over time, that raises the chance that a cell will grow out of control and become cancer.

Because the change is inherited, it is present from birth and can be passed from a parent to a child.

Lynch syndrome makes the body's DNA "spell-check" less reliable, which raises cancer risk.

The cancers it affectsExplain▾

The two cancers most linked to Lynch syndrome are:

• Colorectal cancer, cancer of the colon or rectum
• Endometrial (uterine) cancer, cancer of the lining of the uterus

Lynch syndrome can also raise the risk of some other cancers, such as ovarian and stomach cancer, among others. A key feature is that these cancers often appear earlier in life than they would in the general population.

Signs it might run in your familyExplain▾

Cancer can appear in a family for many reasons, but certain patterns make an inherited condition like Lynch syndrome more likely. Talk with a doctor or genetic counselor if your family has:

• Several relatives with colorectal or endometrial cancer
• These cancers diagnosed at younger ages, such as colon cancer before 50
• The same person having more than one related cancer
• A combination of colon and endometrial cancer across close relatives

When possible, testing often starts with a relative who has had cancer, since that gives the clearest information for the whole family.

Early ages and repeating patterns of colon and uterine cancer are the classic red flags.

How it is foundExplain▾

Lynch syndrome is confirmed with genetic testing, usually from a blood or saliva sample, after a genetic counselor or doctor reviews your history.

Sometimes the path starts with the tumor. A person's cancer may be tested for features that suggest Lynch syndrome. If those features are present, inherited-risk testing follows to see whether the change was passed down.

A positive result means a higher risk of certain cancers — not that cancer is certain. Some people with Lynch syndrome never develop cancer.

What it means for screeningExplain▾

The biggest benefit of knowing you have Lynch syndrome is that it changes your screening plan. People with Lynch syndrome usually:

• Start colorectal screening younger than average-risk adults
• Screen more often, often with colonoscopy

Colonoscopy is especially valuable here because it can find and remove polyps before they become cancer, so screening can prevent cancer as well as catch it early.

Depending on the specific gene involved and personal history, screening or other steps for endometrial cancer and other related cancers may also be recommended.

For Lynch syndrome, earlier and more frequent screening is the main way to lower the danger.

Family and next stepsExplain▾

Because Lynch syndrome is inherited, a diagnosis carries information for your blood relatives. Siblings, children, and parents may share the same change and could benefit from testing and tailored screening.

A genetic counselor can help you understand your result, plan your own screening, and think through how to share the information with family. If Lynch syndrome runs in your family, your care team can build a screening schedule that fits your specific risk.