Hereditary Cancer Syndromes: An Overview

This page is for anyone whose family has several cases of cancer and wonders whether an inherited syndrome is behind it. It explains what these syndromes are, the warning signs, and how they are confirmed.

A hereditary cancer syndrome is a rare inherited condition. It is also called a family cancer syndrome. In it, family members carry a higher-than-average risk of one or more types of cancer. The cause is an inherited change in a cancer-related gene.

The National Cancer Institute notes that up to 10 percent of all cancers may be caused by inherited genetic changes. The vast majority happen by chance, as DNA changes build up over a lifetime. They are not caused by a syndrome.

These syndromes raise the risk of certain cancers. They are uncommon, and they are not a diagnosis of cancer.

In a hereditary cancer syndrome, a harmful change in a cancer-related gene is inherited. It is present in every cell from birth, and it can pass from a parent to a child. With some syndromes, cancers tend to show up at early ages. Some also come with other health conditions that are not cancer.

Inheriting such a change raises risk for a specific reason. The person needs fewer additional DNA changes for a cell to turn cancerous. But they may never develop those changes. And they may never develop cancer.

A few well-known examples show the range:

• Hereditary breast and ovarian cancer, linked to inherited changes in BRCA1 and BRCA2. These raise the risk of breast, ovarian, and several other cancers.
• Lynch syndrome, which raises the risk of colorectal and endometrial cancer, plus some others. The cancers often come at younger ages.
• Familial adenomatous polyposis (FAP), caused by inherited changes in the APC gene. People with FAP have a very high chance of colorectal cancer at an early age. They are at risk of some other cancers too.

Cancer can look like it "runs in a family" for reasons that have nothing to do with an inherited syndrome. The National Cancer Institute points to several:

• Chance. Common cancers can turn up in several relatives by chance alone.
• Shared habits and environment. Relatives may share tobacco use, diet, or exposures such as air pollution. Those can lead to similar cancers.
• Many small-effect changes. A family may share a mix of many genetic variants that each add a tiny bit of risk, rather than one strong syndrome.

So a family history of cancer is a clue worth exploring. It is not proof of a syndrome.

Some patterns make an inherited syndrome more likely. They are worth raising with a doctor or genetic counselor:

• Cancer diagnosed at unusually young ages
• Several relatives with the same type of cancer
• One person having more than one cancer
• Cancer in paired organs, such as both breasts
• Rare cancers, such as male breast cancer

The more of these show up, the more it may be worth looking into.

Finding a syndrome can change a prevention and screening plan. You might be checked at younger ages, or more often. You might consider steps to reduce risk. And because the change is inherited, the information can matter for blood relatives too.

Genetic counseling helps you work out whether your family history fits a syndrome. It helps you decide whether testing makes sense. And it explains what any result would mean for you and your family.

Say a family pattern raises the possibility of a syndrome. A genetic counselor or doctor then reviews the personal and family history. They may suggest genetic testing, usually from a blood or saliva sample. Where possible, testing often begins with a relative who has had cancer, because that gives the clearest information for the whole family.

A confirmed syndrome does not change what you can do overnight. But it does sharpen the plan. It clarifies which cancers to watch for, when to start screening, and which relatives might gain from learning their own risk. A syndrome raises risk; understanding it is what turns that risk into a plan.