Variant of Uncertain Significance (VUS)

Your report says "variant of uncertain significance." Most people read that as bad news. It is not news at all yet.

The National Cancer Institute defines a VUS as a genetic change with not enough data available to know whether it raises cancer risk. The National Human Genome Research Institute says much the same. A variant was found, and it is unclear whether it connects to any health condition.

Labs sort variants into five groups:

• Pathogenic, meaning harmful
• Likely pathogenic
• Uncertain significance
• Likely benign
• Benign, meaning harmless

A VUS sits in the middle. It is not a positive result. It is a result the lab could not call.

Think of it as an unfinished sentence, not a verdict. The gene may be famous. The variant is not.

This is the single most useful fact on this page, and it is rarely said clearly enough.

NCI states that a VUS may be reclassified in future as researchers learn more, and that most often a VUS is reclassified as benign. Benign means it does not raise cancer risk.

So the base rate is on your side. A VUS is far more likely to end up as nothing than as something.

That does not mean ignore it. It means do not let it run your decisions while it is still unfinished.

VUS results are not spread evenly across the population, and the reason has nothing to do with the person.

NHGRI notes that far more genomic data exists for people of European ancestry. Because labs compare your variant against what is already known, having less reference data for your background makes an uncertain result more likely.

If you are Black, Asian, Hispanic, Indigenous, or of mixed ancestry, a VUS may say more about the gaps in genetic databases than about your genes. It is worth naming with your genetics team, and worth asking whether the lab re-reviews results as its data improves.

Here is the hard part. People act on VUS results. They should not.

A VUS should not by itself drive an irreversible decision. That includes risk-reducing mastectomy, removal of ovaries, a more extensive operation than your cancer needs, or a different surgical choice made in a rush.

CDC puts the logic plainly in its Lynch syndrome guidance: the test found a change in a gene linked to the condition, but doctors do not know whether that change causes cancer. You cannot base an operation on that.

Decisions of that size rest on things that are known. Your own diagnosis. Your family history. Your age. Variants that are actually known to be harmful.

There is one question that cuts through all of this. Ask your team:

"Would your advice be any different if this line were not on my report?"

If the answer is no, then the VUS is not driving your care. Your history is. That is how it should be.

If the answer is yes, ask which guideline supports that, and ask to see a genetic counselor before you agree to anything permanent.

Families often want to test everyone at once. With a VUS, that causes harm without producing information.

CDC's guidance is direct: family members usually should not be tested until doctors work out whether the VUS causes cancer. A relative who tests "positive" for an uncertain variant has learned nothing, and may now carry the worry, and may face questions on insurance forms.

There is one exception, and it is not the same thing. Genetics teams sometimes test specific relatives to help the lab classify the variant. That is research into the variant, not a risk test for the relative. It is arranged through genetics, with counseling, and the purpose is explained in advance.

If someone suggests testing your children on the basis of a VUS, ask for a genetics referral first.

The word "variant" appears on two very different reports, and people mix them up constantly.

NCI distinguishes them. Testing for inherited cancer risk, called germline testing, looks at the genes you were born with. Tumor testing looks at changes that happened during your lifetime, inside the cancer itself.

A VUS on a tumor report is usually about whether a treatment might work. A VUS on a germline report is about inherited risk and about your family. The follow-up is different for each.

Ask which one you had. If your report mentions both, ask for the germline part to be explained separately.

Variants get reclassified as evidence accumulates. The problem is that the update has to find you, sometimes years later, and the system for that is weak.

Take these steps:

• Get a full copy of the lab report. Not a summary. It should name the gene, the exact variant in the lab's own notation, the laboratory, and the date.
• Ask who is responsible for telling you if the classification changes. The lab, the ordering clinician, or nobody.
• Make sure the ordering clinic and the laboratory have current contact details for you. Update them when you move or change clinician.
• Ask whether you can request a re-review, and roughly how often that is worth doing.
• Keep your family history updated with the genetics service. New cancers in the family can change how a variant is interpreted.

• Which gene is this in, and what is the exact variant?
• Was this germline testing, tumor testing, or both?
• What does my personal and family history suggest on its own, ignoring this variant?
• What screening would you recommend for me either way?
• Who will contact me if this is reclassified, and how?
• Should any of my relatives see a genetic counselor now?

• Genetic Testing for Inherited Cancer Susceptibility Syndromes — National Cancer Institute
• Cancer Genetics Overview (PDQ) — National Cancer Institute
• Variant of Uncertain Significance (VUS) — National Human Genome Research Institute
• Genetic Testing for Lynch Syndrome — Centers for Disease Control and Prevention
• What do the results of genetic tests mean? — MedlinePlus Genetics