Research
Does Cancer Run in Families? Understanding Hereditary Cancer and Genetic Testing
News about BRCA genes and genetic testing can make it seem like cancer is simply inherited. Here's what NCI says about hereditary cancer risk and what testing can tell you.
Please note: this page is educational only — it is not medical advice, and it does not speculate about anyone’s health beyond reliable public reporting. For questions about your own health, talk with your healthcare team.
What people see in the news
Stories about the BRCA genes, at-home DNA kits, and celebrities choosing genetic testing can leave the impression that cancer is mostly inherited, or that a home test can tell you whether you'll get it. The truth is more measured, and understanding it can ease a lot of worry.
What it actually means
According to the National Cancer Institute, about 5% to 10% of all cancers are thought to be caused by harmful genetic changes inherited from a parent. Genetic testing for inherited cancer risk looks for specific inherited changes (sometimes called mutations or pathogenic variants) in a person's genes that may increase the risk of diseases such as cancer.
NCI also explains that cancer can appear to run in a family even without an inherited genetic change. A shared environment or behavior, such as tobacco use, can cause similar cancers among relatives. But certain patterns — the types of cancer, the ages at which they develop, and other conditions — may suggest an inherited change is at play.
Importantly, NCI distinguishes this from tumor genetic testing (biomarker testing) done to guide treatment. Testing for inherited risk looks at genes you were born with; tumor testing looks at changes that arose during a person's lifetime.
NCI notes that genetic counseling is generally recommended before any testing for inherited cancer risk, and results can be positive, negative (including a "true negative" or "uninformative negative"), or a variant of uncertain significance — a change for which there isn't yet enough data to know whether it raises risk.
What to keep in mind
- Most cancers are not inherited. NCI puts the inherited share at roughly 5% to 10%.
- A positive result means increased risk, not certainty of developing cancer; a negative result doesn't always mean zero risk.
- On at-home tests, NCI cautions that the only FDA-approved direct-to-consumer test for inherited cancer risk checks just three BRCA variants common in people of Ashkenazi Jewish descent, and about 80% of cancer-causing BRCA variants are missed by that approach.
- Laws like GINA offer some protection against genetic discrimination in health insurance and employment, though NCI notes GINA does not cover life, disability, or long-term care insurance, or members of the military.
Questions to ask a healthcare team
- Does my personal or family history suggest I should consider genetic testing?
- What would a positive, negative, or uncertain result actually mean for me?
- Should I speak with a genetic counselor before deciding?
- How might my results affect my blood relatives?
Knowing that inherited cancer is the exception, not the rule, can make family-history worries feel more manageable. Free, plain-language cancer education helps more people understand what genetic testing can and can't tell them.