Understanding Genes, Family Risk, Genetic Testing & Screening
When someone in a family is diagnosed with cancer, one of the first concerns is often:
“Can my children, brothers, sisters, or other relatives also get this cancer?”
The most important point is:
Cancer itself is not passed from one family member to another. What can sometimes be inherited is a gene change that increases a person's risk of developing certain cancers.
Here are the most common questions families ask.
1. Can cancer be inherited from parents?
Not exactly.
You do not inherit the cancer itself . However, some people inherit a harmful genetic change that makes them more likely to develop certain cancers during their lifetime.
Every person receives approximately half of their genetic information from their mother and half from their father.
Genes act like an instruction book for the body. They help control how cells grow, divide and repair damage.
Sometimes a person is born with a harmful change in a gene that normally helps protect against cancer. This is called an inherited or germline pathogenic variant .
If this genetic change can pass from parent to child, an increased tendency to develop certain cancers may appear repeatedly within a family.
But remember:
Inheriting a cancer-predisposition gene does not mean that you will definitely develop cancer. It means your risk may be higher than usual.
Only about 5–10% of cancers are generally estimated to result directly from inherited harmful genetic changes.
Therefore, most cancers are not hereditary .
2. Is hereditary cancer the same as cancer spreading in the body?
No. These are completely different things.
When cancer spreads from one part of a patient's body to another—for example, breast cancer spreading to the liver—it is called metastasis .
Hereditary cancer refers to an inherited genetic predisposition that can increase cancer risk within a family.
Cancer cells themselves are not passed from a parent to a child.
3. What is an easy example of hereditary cancer?
BRCA-associated hereditary cancer is a well-known example.
Suppose a woman develops breast cancer and is found to carry an inherited harmful change in the BRCA1 or BRCA2 gene .
She does not pass breast cancer itself to her children.
She may, however, pass the altered BRCA gene to a daughter or a son .
If they inherit it, their lifetime risk of developing certain cancers can be substantially higher than that of the general population.
Importantly, cancer-predisposition genes can come from either side of the family .
Your father's family history can be just as important as your mother's.
4. Which cancers are associated with BRCA1 and BRCA2?
Inherited pathogenic variants in BRCA1 and BRCA2 are associated with increased risks of several cancers.
In women, these particularly include:
Breast cancer
Ovarian/fallopian-tube cancer
Pancreatic cancer
In men, they can include:
Prostate cancer
Male breast cancer
Pancreatic cancer
Therefore, a history of ovarian cancer in a mother or sister may be relevant when assessing another relative's risk of breast, prostate or other BRCA-associated cancers.
5. Can colorectal and uterine cancers run together in families?
Yes. One important cause is Lynch syndrome .
Lynch syndrome results from inherited abnormalities involving DNA mismatch-repair genes.
It particularly increases the risk of:
Colorectal cancer
Endometrial/uterine cancer
It can also increase the risk of certain ovarian, gastrointestinal, urinary-tract and other cancers.
Therefore, a family containing multiple cases of colorectal and endometrial cancer—particularly when cancers occur at younger ages—may need hereditary cancer assessment.
6. What is Familial Adenomatous Polyposis?
Familial Adenomatous Polyposis (FAP) is an inherited condition usually caused by a pathogenic variant in the APC gene .
Affected individuals can develop hundreds or even thousands of colorectal polyps, often beginning relatively young.
Without appropriate surveillance and preventive treatment, their lifetime risk of colorectal cancer becomes extremely high.
FAP demonstrates why identifying hereditary cancer risk can be so valuable:
Doctors may be able to intervene before cancer develops.
7. What is Li-Fraumeni syndrome?
Li-Fraumeni syndrome is a hereditary cancer-predisposition syndrome usually caused by an inherited pathogenic variant in the TP53 gene .
It can predispose people to several different cancers, sometimes at unusually young ages, including:
Breast cancer
Soft-tissue sarcoma
Bone sarcoma
Brain tumours
Adrenocortical cancer
Leukemia
Several other malignancies
Therefore, several relatives developing different types of cancer at unusually young ages can sometimes be an important clue to an inherited cancer syndrome.
8. Are there other hereditary cancer syndromes?
Yes.
Other inherited syndromes can predispose people to cancers such as:
Retinoblastoma — RB1
Kidney cancer — for example, VHL-associated syndromes
Medullary thyroid cancer — RET/MEN2
Melanoma — certain familial melanoma syndromes
Gastric cancer — hereditary diffuse gastric cancer
Endocrine tumours — MEN syndromes
Certain sarcomas and childhood cancers
Inherited predisposition can be particularly important in certain childhood tumours, such as retinoblastoma.
9. When should we suspect that cancer may run in a family?
One relative developing cancer—particularly at an older age—does not automatically mean that the family has a hereditary cancer syndrome.
Doctors become more suspicious when there is a recognizable pattern.
Important clues can include:
Cancer occurring at an unusually young age
Several close blood relatives developing the same or related cancers
Cancer appearing across successive generations
One person developing two or more separate primary cancers
Cancer affecting both paired organs, such as both breasts
Male breast cancer
Ovarian cancer
Pancreatic cancer
Metastatic or certain high-risk prostate cancers
Colorectal cancer at a young age
Colorectal and endometrial cancers occurring within the same family
A relative already known to carry an inherited cancer-associated pathogenic variant
These findings do not prove that a hereditary cancer syndrome is present.
They indicate that formal hereditary-risk assessment and genetic counseling may be appropriate.
10. If my parent had cancer, will I also develop cancer?
Not necessarily.
Even when an inherited cancer-predisposition gene is present in a family, inheriting the gene does not necessarily mean that cancer will develop.
Different genetic syndromes have different levels of cancer risk.
Your individual risk depends on factors including:
Which gene is involved + which variant is present + your age + sex + family history + other biological and environmental factors
This is why genetic results should be interpreted in the context of appropriate genetic counseling and medical advice.
11. Why should healthy relatives undergo cancer screening?
Because screening looks for cancer before symptoms appear .
A person may feel completely healthy while an early cancer or precancerous abnormality is developing.
If doctors know that someone has a higher-than-average inherited risk, screening may need to be:
Started earlier
Performed more frequently
Performed using additional or different investigations
The purpose is not to frighten healthy relatives.
The purpose is to identify cancer—or, in some conditions, a precancerous abnormality—at an earlier stage when treatment may be easier and outcomes may be better.
12. Does every relative of a cancer patient need genetic testing?
No.
Most cancers are not caused by hereditary cancer syndromes.
Therefore, relatives do not automatically need genetic testing simply because one person in their family developed cancer.
Doctors consider the overall pattern:
Type of cancer + age at diagnosis + number of affected relatives + maternal family history + paternal family history + tumour characteristics + multiple cancers in one individual
When hereditary cancer is suspected, genetic counseling can help determine whether testing is appropriate.
Whenever possible, genetic testing generally begins with the family member who has developed cancer .
If a disease-causing inherited variant is identified, appropriate blood relatives may then undergo targeted testing for that particular familial variant.
13. Are genetic testing and cancer screening the same thing?
No. They answer two different questions.
Genetic testing
Usually performed using blood or saliva.
It asks:
“Was I born with a genetic change that increases my risk of certain cancers?”
Cancer screening
Depending on a person's age, sex and individual risk, screening may include investigations such as:
Mammography
Breast MRI
Colonoscopy
Cervical cancer screening
Other cancer-specific investigations
Screening asks:
“Is there currently an early cancer or precancerous abnormality that can be detected before symptoms develop?”
A genetic result can therefore help doctors determine which screening tests are appropriate, when they should begin and how frequently they should be performed.
14. If my genetic test is positive, does that mean I have cancer?
No.
A positive hereditary cancer test usually means:
“You inherited a genetic change that increases your risk of developing certain cancers.”
It does not mean:
“You currently have cancer.”
Depending on the gene involved, your age, sex, family history and magnitude of risk, doctors may recommend:
Increased surveillance
Earlier screening
Additional screening methods
Risk-reduction measures
Medicines in selected situations
Preventive surgery in carefully selected high-risk situations
The appropriate strategy varies considerably between hereditary cancer syndromes.
15. If my genetic test is negative, am I completely safe from cancer?
No.
Most cancers are not caused by a single inherited cancer-predisposition gene.
Cancer can still develop because of many factors, including:
Increasing age
Tobacco exposure
Alcohol
Obesity
Certain infections
Environmental exposures
Acquired genetic changes
Other biological and lifestyle factors
Therefore, a negative hereditary cancer test does not mean that routine cancer screening can be ignored.
Appropriate population-based screening remains important.
16. Which relatives should I mention when giving my family history?
Tell your doctor about cancers occurring in blood relatives on both sides of your family .
This can include:
Parents → Brothers/Sisters → Children → Grandparents → Aunts/Uncles → Nieces/Nephews → Cousins
Your father's family history matters just as much as your mother's family history.
Whenever possible, provide three pieces of information:
Who developed cancer → What cancer they had → Approximately what age they were diagnosed
For example:
Mother → Breast cancer → Age 42
is much more informative than simply saying:
“Cancer runs in our family.”
17. What should I do if several people in my family have had cancer?
Do not assume either that you will develop cancer or that the pattern is unimportant.
Prepare as accurate a family history as possible and discuss it with your doctor.
Depending on the pattern, you may be advised to undergo hereditary-risk assessment or genetic counseling.
The pathway may be:
Family history → Hereditary-risk assessment → Genetic counseling/testing when indicated → Appropriate screening and prevention for relatives
Testing the appropriate person first is important because indiscriminate genetic testing can sometimes produce results that are difficult to interpret.
18. What is the most important message for families?
You generally do not inherit cancer itself. You may occasionally inherit a genetic change that increases your risk of developing cancer.
Only a minority of cancers—approximately 5–10% —are thought to result directly from inherited harmful genetic changes.
Having a cancer-predisposition gene does not guarantee that cancer will develop.
Similarly, having no known hereditary pathogenic variant does not make someone immune to cancer .
But when hereditary cancer risk is identified, it can sometimes help protect several members of the same family through appropriate surveillance, screening and preventive strategies.
Remember
Know your family history. Share it with your doctor. Screen appropriately.
One person's cancer diagnosis can sometimes provide an opportunity to recognize increased risk in healthy relatives and take preventive action before cancer develops.