The short answer
Two different tests are both called genetic. Tumor DNA testing, also called biomarker or somatic testing, looks at changes in a person's cancer to help guide treatment. Inherited (germline) testing looks for changes present from birth that raise cancer risk and can be passed to relatives. Sometimes a tumor test uncovers an inherited change, which a germline test can then confirm.
Tumor DNA (biomarker) testing looks at changes in a person's cancer to guide treatment.
Inherited (germline) testing looks for changes present from birth that raise cancer risk.
Tumor testing uses a sample of cancer cells; germline testing uses blood or saliva.
Acquired changes found in a tumor are not passed to family members.
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The full explanation.
The simple version
The word "genetic" gets attached to two very different cancer tests, and mixing them up causes confusion.
- Tumor DNA testing (also called biomarker or somatic testing) looks at changes in a person's cancer to help guide treatment.
- Inherited (germline) testing looks for changes present in every cell from birth that raise cancer risk and can be passed to relatives.
Same word, different questions: one is about treating a cancer, the other is about inherited risk.
Tumor DNA (biomarker) testing
Biomarker testing is for people who have cancer. It looks for genes, proteins, and other markers in the cancer that can affect how treatments work. Each person's cancer has its own pattern of biomarkers.
Key points from the National Cancer Institute:
- The sample is a piece of the cancer — from a biopsy, from surgery, or sometimes from a blood-based liquid biopsy.
- The changes it finds are mostly acquired (somatic) changes that arose during life, which cause most cancers and cannot be passed to family members.
- Results can guide treatment, because some targeted therapies and immunotherapies only work for cancers with certain biomarkers. Testing can also help find a clinical trial a person may be able to join.
Biomarker testing goes by several names, including tumor testing, genomic profiling, molecular profiling, and somatic testing.
Inherited (germline) testing
Inherited-risk testing asks a different question: were you born with a change that raises your cancer risk?
- The sample is healthy cells — usually blood or saliva — because an inherited change is in every cell.
- A result can guide screening and prevention, and because the change can be passed down, it carries information for blood relatives.
- It can be considered by people with or without cancer.
Where the two overlap
The line is not always sharp. Some biomarker tests compare a tumor with a person's healthy cells, and a tumor test can sometimes reveal a change the person was born with. When that happens, the National Cancer Institute notes that a separate germline test is usually recommended to confirm whether the change is truly inherited — because that matters for the person's future risk and for their family. Learning that an inherited change is present may lead a provider to suggest speaking with a genetic counselor.
Which is which, at a glance
- Goal: tumor testing guides treatment; germline testing assesses inherited risk.
- Sample: tumor testing uses cancer cells; germline testing uses blood or saliva.
- Passed to family? tumor (somatic) changes usually are not; inherited (germline) changes can be.
- Who: tumor testing is for people with cancer; germline testing can be for people with or without cancer.
Cost and coverage, in brief
Cost can shape which testing happens. For biomarker (tumor) testing, the National Cancer Institute notes that the price varies widely by the type of test, the cancer, and the insurance plan. Some biomarker tests are covered by Medicare and Medicaid for people with advanced cancer, and private insurers often cover a test when there is enough proof it is needed to guide treatment.
Inherited (germline) testing and counseling are also typically covered by health insurance when considered medically necessary, though coverage varies. Checking with your provider and insurer beforehand helps avoid surprises, and some programs offer testing at reduced or no cost for people who qualify.
A calm way to think about it
Both tests can be useful, but they are not interchangeable. Knowing which question you are trying to answer — how to treat a cancer, or whether an inherited risk is present — points to the right test. A doctor or genetic counselor can explain which one fits your situation and what its results would mean.
Words to know
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Common questions
▸What is the difference between tumor testing and inherited genetic testing?
Tumor testing, also called biomarker or somatic testing, looks for changes in a person's cancer cells to help choose treatment. Inherited (germline) testing looks for changes present in every cell from birth that raise cancer risk and can be passed to relatives. They answer different questions.
▸What sample does each test use?
Tumor testing uses a sample of cancer cells, from a biopsy, surgery, or sometimes a blood-based liquid biopsy. Inherited testing uses a sample of healthy cells, usually blood or saliva, because an inherited change is present in every cell of the body.
▸Are the changes found in a tumor passed to children?
Usually not. Most changes found in a tumor are acquired (somatic) changes that happened during life and cannot be passed on. Inherited changes, present from birth, are the ones that can be passed to children.
▸Can a tumor test reveal an inherited change?
Yes. A tumor test can sometimes find a change that a person was born with. If that happens, a separate germline test is usually recommended to confirm whether the change is truly inherited, because that matters for the person and their relatives.
▸Why does biomarker testing matter for treatment?
Some treatments, including certain targeted therapies and immunotherapies, only work for cancers with specific biomarkers. Biomarker testing can show whether a person's cancer has a change that a matching treatment targets, or help find a clinical trial they may be able to join.
▸Which test would I get?
It depends on the goal. People who have cancer may get tumor testing to help guide treatment. People concerned about inherited risk, whether or not they have cancer, may consider germline testing. A doctor or genetic counselor can explain which fits your situation.
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