The short answer
Cancer is a genetic disease, but the gene changes behind it come in two kinds. Inherited changes are present in every cell from birth and can be passed to children. Acquired changes happen during life from chance, aging, or carcinogens, and are not passed on. The vast majority of cancers come from acquired changes; up to 10 percent are linked to inherited ones.
Cancer is caused by changes in genes that control how cells grow.
Inherited (germline) changes are present in every cell from birth and can be passed to children.
Acquired (somatic) changes happen during life and are not passed to children.
Acquired changes cause the vast majority of cancers.
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The full explanation.
The simple version
Cancer is a genetic disease — it is caused by changes in genes that control how cells grow and multiply. But those changes come in two kinds, and telling them apart matters.
- Inherited changes are present in every cell from birth and can be passed to children.
- Acquired changes happen during life and are not passed on.
Most cancers come from acquired changes; a smaller share is linked to inherited ones.
Inherited (germline) changes
An inherited change, also called a germline change, is passed down from a parent. Because it was present in the egg or sperm cell, it ends up in every cell of the body from the start of life.
That is why a person can carry the change without having cancer — and why a simple blood or saliva sample can reveal it. It also means the change can be passed to children, so it carries information for the whole family. The National Cancer Institute notes that up to 10 percent of cancers may be caused by inherited changes.
Acquired (somatic) changes
An acquired change, also called a somatic change, happens during a person's life. It can come from:
- Random errors as cells copy their DNA and divide
- Aging, as changes build up over many years
- Carcinogens in the environment, such as chemicals in tobacco smoke, UV rays from the sun, or certain viruses
These changes are found only in the cells where they occurred — including tumor cells — and are not present in egg or sperm cells. So acquired changes cannot be passed to children. The vast majority of cancers arise this way, as changes accumulate over time and eventually turn a healthy cell cancerous.
Why the difference matters
The two kinds of change are found by different tests that answer different questions:
- To look for an inherited change, a test uses a sample of healthy cells, usually blood or saliva. A result can guide screening and prevention and can matter for blood relatives.
- To find acquired changes in a cancer, a test uses a sample of the tumor itself. This can help guide treatment choices.
Because the samples and goals differ, knowing which kind of change is in question helps a care team choose the right test.
An important overlap
The line is not always sharp. Sometimes a tumor test picks up a change that a person was actually born with. When that happens, a separate inherited-risk (germline) test can confirm whether the change was truly inherited — which matters for the person's future risk and for their relatives.
Inheriting a change is not a diagnosis
Inheriting a cancer-related change raises risk but does not guarantee cancer. A person with an inherited change needs fewer additional DNA changes for a cell to become cancerous, but they may never develop those changes, and may never develop cancer.
Where each kind shows up
Another way to keep the two straight is to think about where the change lives. An inherited change is in every cell — skin, blood, and tumor alike — because it was there from the very first cell. An acquired change is only in the cells that descended from the one where it happened, such as the cells of a tumor.
That is why a blood or saliva sample can reveal an inherited change but usually will not show the acquired changes that are unique to a tumor. To see those, a sample of the cancer itself is needed. The location of the change shapes which test can find it.
A calm way to think about it
Two people can hear the words "genetic change" and mean very different things — one born with, one acquired over a lifetime. Understanding which is which helps make sense of test results, family risk, and treatment options. A doctor or genetic counselor can explain which kind of change applies to your situation and which test, if any, fits.
Words to know
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Common questions
▸What is the difference between inherited and acquired gene changes?
Inherited changes, also called germline changes, are present in every cell of the body from birth and can be passed from a parent to a child. Acquired changes, also called somatic changes, happen during a person's life and are found only in certain cells; they are not passed to children.
▸Which kind causes most cancers?
Acquired changes cause the vast majority of cancers. They build up over many years from random errors when cells divide, from aging, and from carcinogens such as tobacco smoke or UV rays. Up to 10 percent of cancers are linked to inherited changes.
▸Are acquired gene changes passed to children?
No. Acquired changes are not present in egg or sperm cells, so they cannot be passed on. An inherited change can be passed on because it is present in a parent's egg or sperm cell.
▸Why does the difference matter?
It changes what a test looks for. A blood or saliva test can find an inherited change and can carry information for blood relatives. Testing a sample of the tumor finds acquired changes that can help guide treatment. The two tests answer different questions.
▸If I inherit a cancer-related change, will I get cancer?
Not necessarily. Inheriting a change raises risk but does not guarantee cancer. People with an inherited change need fewer additional DNA changes to develop cancer, but they may never develop those changes or the disease.
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