My father had cancer. Will I get it?

It depends on which cancer and how old he was. Lung cancer at 72 after decades of smoking says little about your genes. Bowel cancer at 45, or breast cancer in a man, is worth taking to a doctor or genetic counsellor, because it can point to an inherited gene.

Is breast cancer inherited from the mother or the father?

From either. BRCA1 and BRCA2 are not on the sex chromosomes, so a father passes them to his daughters exactly as often as a mother does. Because men who carry them usually stay well, a father's side is the one families most often forget to count.

Does cancer skip a generation?

The gene does not skip, but its effects can. Many carriers — especially men with BRCA changes — never develop cancer, so a family can look as if it skipped someone. Each of that person's children still had a 50% chance of inheriting it.

Should I have a genetic test for cancer risk?

It is worth discussing if your family shows the warning signs on this page. Testing works best when it starts with a relative who had cancer. Once their change is known, everyone else can be tested for that one change, and a negative result then means something.

Can a home DNA kit tell me if I carry a cancer gene?

Not reliably. Most consumer kits check only a handful of specific changes, so a clear result can easily miss the one your family carries. A clinical test ordered through a doctor or genetic counsellor looks at the whole gene.

Is lung cancer hereditary?

Mostly not. Smoking and second-hand smoke explain most lung cancer, and families often share both. Family history raises the risk somewhat even in people who never smoked, but lung cancer on its own is rarely a sign of an inherited cancer syndrome.

Is Cancer Hereditary? When a Family History Points to a Gene

Inherited, familial, or just common: three different things

When people say cancer “runs in the family”, they can mean three quite different things.

Inherited (hereditary) cancer. A single harmful gene change, passed down from a parent, raises the risk of particular cancers a great deal. This is about 5–10% of all cancer. Each child of a carrier has a 50% chance of inheriting it, sons and daughters alike — the dominant pattern.
Familial cancer. A family has more cancer than expected, but no single gene explains it. Many small genetic effects add up, and families also share smoking, diet, weight and infections. The risk to relatives is raised, but far less than with an inherited gene.
Chance. Roughly one person in two or three develops cancer at some point in their life. Two grandparents with cancer in their 70s is what most families look like.

Telling these apart is the whole point of looking at your family. It changes whether you need genetic testing, earlier screening, or just the screening everyone gets.

Warning signs that a cancer may be inherited

These are the patterns the US National Cancer Institute lists as suggesting a hereditary cancer syndrome:

Cancer at a young age — for example, bowel cancer or breast cancer before 50.
Several close relatives with the same cancer, or with cancers that go together, on the same side of the family:
- breast, ovarian, pancreatic or prostate cancer — the BRCA pattern (more on BRCA);
- bowel, womb (endometrial), ovarian or stomach cancer — the Lynch syndrome pattern (more on Lynch syndrome).
One person with two or more separate cancers.
Cancer in both of a pair of organs — both breasts, or both kidneys.
An unusual cancer, such as breast cancer in a man or ovarian cancer — or cancer alongside birth differences known to go with a cancer syndrome.
A relative who has already tested positive for a cancer gene change.
Ancestry with known founder variants, such as Ashkenazi Jewish ancestry, together with any of the above.

One of these on its own is not proof. Two or three together is a reason to ask for genetic counselling.

Your risk when a relative had a common cancer

For the three common cancers with the best family data, this is what a close relative’s diagnosis does on average:

Your relative	Your risk, compared with no family history
Mother or sister with breast cancer	about 1.8 times — by 80, about 13% instead of 8%
Two first-degree relatives with breast cancer	about 2.9 times — by 80, about 21%
Parent, brother or sister with bowel cancer	about 2.2 times
Two or more with bowel cancer	about 4 times
Father with prostate cancer	about 2.3 times
Brother with prostate cancer	about 3.1 times

Two things are worth holding on to. The risk is higher when the relative was young at diagnosis. And most people with a family history never develop that cancer — in the largest analysis of breast cancer in families, about eight in nine women who developed it had no affected mother, sister or daughter.

Which side of the family counts

Both sides count, but count them separately. Three relatives with cancer on your mother’s side and none on your father’s is a different pattern from one on each side — and only the first suggests a gene.

The father’s side is the one families forget. Genes such as BRCA1 and BRCA2 pass through men exactly as often as through women, but the men who carry them often stay well. A father’s sisters and mother matter as much as your own mother’s family.

What changes if your risk is raised

Screening starts earlier. With a parent or sibling who had bowel cancer, colonoscopy is often advised from 40, or ten years before the age your relative was diagnosed. With a strong breast cancer history, screening may start younger and include MRI. The exact rules differ between countries, so ask for your own.

Genetic counselling and testing. If the pattern fits an inherited syndrome, the best first test is usually on the relative who had cancer. Finding their change turns everyone else’s test into a simple yes-or-no for that one change.

If you do carry a gene change, the options range from more frequent screening to medicines or surgery that lower the risk. Carriers of Lynch syndrome genes, for example, have colonoscopies every one to two years, which catches bowel cancer early or prevents it.

If you do not, a negative test for your family’s known change usually means your risk goes back to about average for that gene — and you cannot pass it to your children.