Lynch Syndrome: Inherited Colorectal and Other Cancer Risk

This page covers the basics of Lynch syndrome: how it works, which cancers it affects, family warning signs, and what it means for screening.

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

Lynch syndrome most often raises the risk of colorectal cancer (colon and rectum). It also raises the risk of endometrial cancer, which affects the lining of the uterus. It can raise the risk of some other cancers too. When cancer develops in people with Lynch syndrome, it typically occurs in their 40s or 50s.

Lynch syndrome raises cancer risk — but knowing about it opens the door to frequent screening that can find precancer or early-stage cancer.

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

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

The change is inherited. So it is there from birth, and it can pass from a parent to a child.

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

Lynch syndrome is not something a person catches. It is not something habits bring on later. It is an inherited change, carried in every cell of the body from the start of life. Because it is inherited, each close blood relative may or may not carry the same change.

That sets it apart from cancers that seem to run in families for other reasons, such as shared habits or chance.

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

Other cancers, such as ovarian and stomach cancer, can also be more likely. When cancer develops, it typically occurs in the 40s or 50s.

Cancer can show up in a family for many reasons. But some 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
• A mix of colon and endometrial cancer across close relatives

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

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

Lynch syndrome is confirmed with genetic testing, usually from a blood or saliva sample. It follows a review of your history by a genetic counselor or doctor.

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

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

A big benefit of knowing you have Lynch syndrome is that it can change your screening plan. NCI notes that current prevention methods include frequent cancer screenings to find precancer or early-stage cancer.

Which tests you have, when you start, and how often depends on the specific gene involved and on your own history. Your care team will build the plan with you.

For Lynch syndrome, a screening plan built by your care team is the main way to find problems early.

Lynch syndrome is inherited, so a diagnosis carries information for your blood relatives. Siblings, children, and parents may share the same change. They could benefit from testing and a screening plan of their own.

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