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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Gastroenterology

What Does a VUS Genetic Test Result Mean for FAP Care?

At a Glance

A VUS in APC does not confirm or rule out FAP, and a single MUTYH VUS does not establish MAP. Doctors base screening and surgery on polyp burden, polyp features, and personal and family history, while the laboratory may update the result later.

A Variant of Uncertain Significance (VUS) means that your genetic test found a change in your DNA, but scientists do not yet have enough information to know if this change causes a disease or if it is just a harmless, normal variation [1][2]. Because a VUS is inconclusive, it should never be the sole reason for making permanent medical or surgical decisions [1].

What a VUS Does—and Does Not—Mean

A VUS result can feel frustrating, but it is important to understand its limits [3][4]:

  • It does not confirm you have FAP. A VUS is not a positive diagnosis.
  • It does not rule out FAP. If you have hundreds of polyps, you may still have a polyposis syndrome regardless of the genetic test result.
  • It cannot be used to test relatives. Because the variant’s meaning is unknown, finding the same VUS in family members does not clarify their cancer risk. Their medical care should be based on their own clinical and family histories.
  • It means different things for the APC vs. MUTYH genes. A variation in the APC gene is investigated for Familial Adenomatous Polyposis (FAP). A variation in the MUTYH gene is investigated for MUTYH-associated polyposis (MAP). MAP generally requires disease-causing variants in both copies of the MUTYH gene [5][6]. A single MUTYH VUS does not establish MAP.

Let Your Clinical Signs Guide Your Care

When a genetic test is inconclusive, your medical team will base your care on your phenotype—your overall clinical features and cancer risk [2][7].

If you have a VUS but no polyps, you will typically follow routine or family-history-based screening rather than an intensive FAP protocol. However, if you have a strong polyposis phenotype, your management plan will be driven by:

  • Cumulative polyp count: The total number of polyps found in your colon over your lifetime [7][8].
  • Polyp characteristics: The size, location, and histology (what the cells look like under a microscope) of the polyps [7][9].
  • Personal and family history: Any history of colon cancer, desmoid tumors, or other FAP-related features in you or your blood relatives [2][8].

If your clinical findings point to a polyposis syndrome, your doctor will recommend regular lower and upper gastrointestinal surveillance (such as colonoscopies and upper endoscopies) based on your specific polyp burden, not the VUS [10][11].

Making Decisions About Surgery

A VUS in a hereditary cancer gene should not be used to direct major clinical decision-making, such as a colectomy (surgical removal of the colon) [1][2].

Instead, surgery is considered when it becomes medically necessary based on your clinical findings. Your care team may recommend surgery if your polyp burden can no longer be safely controlled or removed endoscopically, if high-grade dysplasia (precancerous changes) or cancer develops, or if the disease progresses rapidly [7][12]. You should not rush into surgery because of a VUS, but you also should not delay necessary surgery waiting for a VUS to be reclassified.

Monitoring for Reclassification

Genetics is a rapidly advancing field. Over time, as researchers gather more data, testing laboratories may re-evaluate and “reclassify” a VUS as either pathogenic (disease-causing) or benign (harmless) [13][14]. For example, when expert panels recently applied specialized criteria to APC variants, a significant portion were downgraded to likely benign [13][14].

However, reclassification is not guaranteed, it can take years, and a variant can be upgraded or downgraded. To stay informed:

  • Ask about notification policies: Find out if your genetics clinic or ordering doctor will contact you if an amended report is issued, or if you need to reach out to them [15][16].
  • Keep your contact info current: Ensure your medical team has your up-to-date phone number and address [17][16].
  • Check in periodically: Plan to check in with your genetic counselor or doctor annually or every few years to ask if there are any updates on your variant [15].

Common questions in this guide

Does a VUS mean that I have FAP?
No. A VUS means the genetic change has not been shown to cause disease, so it neither confirms nor rules out familial adenomatous polyposis. Your polyp findings and personal and family history are considered separately.
Can my relatives use my VUS result to find out if they have FAP?
Usually not. Because the meaning of a VUS is unknown, finding the same variant in a relative does not reliably predict that person’s cancer or polyp risk. Relatives should discuss testing and screening with a healthcare professional based on their own medical and family histories.
How is FAP care decided when genetic testing finds a VUS?
Care is based on clinical findings, including the lifetime number of polyps, their size, location, and microscopic features, as well as personal and family history. These findings may determine the schedule for colonoscopy and upper endoscopy even when the genetic result is inconclusive.
Should I have colon surgery because of a VUS?
A VUS alone should not determine whether you have a colectomy. Surgery may be considered when polyps cannot be safely controlled or removed during endoscopy, or when high-grade dysplasia, cancer, or rapid disease progression develops. Do not delay medically necessary surgery while waiting for a VUS update.
Can a VUS be reclassified later?
Yes, a laboratory may eventually reclassify a VUS as disease-causing or benign when more evidence becomes available, but reclassification is not guaranteed and may take years. Ask your genetics clinic how updates are handled, keep your contact information current, and check in periodically.
What is the difference between an APC VUS and a MUTYH VUS?
An APC variant is evaluated in relation to FAP, while a MUTYH variant is evaluated in relation to MUTYH-associated polyposis. A single MUTYH VUS does not establish that condition, and neither type of VUS should be treated as a confirmed diagnosis.

Related questions

What Are Normal Bowel Movements After FAP J-Pouch Surgery? What Is the Spigelman Staging System for FAP Polyps? Can FAP Occur Without a Family History? APC Genetics What Is Life Expectancy With Familial Adenomatous Polyposis? Are Retinal Spots (CHRPE) a Sign of FAP? What to Know
Show more
Can Medications Delay or Replace Colon Surgery for FAP? At What Age Should Preventive Colon Surgery for FAP Be Done? Does Colon Surgery Trigger Desmoid Tumors in FAP Patients? Can My APC Gene Variant Predict FAP Features and Risks? Is Gardner Syndrome Different From FAP? Key Facts Explained What Is the Genetic Difference Between MAP and FAP?

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References

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This page explains how a VUS may affect FAP assessment and care for informational purposes only and does not constitute medical advice. Ask your genetic counselor, gastroenterologist, or surgeon how your own results and clinical findings should guide care.