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Serrated polyposis syndrome: what it is and what the genes tell us | CION Cancer Clinics
Serrated polyposis syndrome is diagnosed when colonoscopy finds many serrated polyps, a type that can slowly turn into bowel cancer. Unlike most polyposis conditions, it is rarely caused by a single inherited gene fault. This page explains how it is recognised, what genetic testing can and cannot find, and what it means for your colonoscopies and for your brothers, sisters and children. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What is serrated polyposis syndrome?
- How is serrated polyposis syndrome diagnosed?
- What happens once the syndrome is diagnosed?
- The words you will meet, in plain language
- What the diagnosis changes, and what it does not
- Four things patients assume, and what is actually true
- What can this page not tell you?
- Common questions about serrated polyposis syndrome
The short answer
What is serrated polyposis syndrome?
Serrated polyposis syndrome is a condition in which many serrated polyps grow in the large bowel. Serrated polyps have a saw-tooth look under the microscope, and some types can slowly turn into bowel cancer. The diagnosis is made from the number, size and position of polyps found at colonoscopy, not from a blood test.
Is it inherited?
Usually not in a simple way. In most people with the syndrome, no single gene fault is found. A small number carry a fault in a gene called RNF43, and a few other genes have been suggested in rare families. Even so, brothers, sisters and children of someone with the syndrome have a higher chance of bowel cancer than other people, so they are offered colonoscopy earlier.
What else raises the chance
Smoking is a recognised risk factor for serrated polyps, and carrying extra weight may add to it. Neither causes the syndrome on its own. But stopping smoking is one of the few changes that sits entirely within your control, and it is worth making.
This diagnosis comes from the colonoscopy and the pathologist's reports, not from the genetics laboratory.Making the diagnosis
How is serrated polyposis syndrome diagnosed?
Doctors use the World Health Organization criteria. Meeting either one of the two is enough.
Larger polyps above the rectum
At least five serrated polyps above the rectum, each at least five millimetres across, with at least two of them a centimetre or more. This is the pattern most people are diagnosed with.
Many polyps of any size
More than twenty serrated polyps of any size spread through the large bowel, with at least five of them above the rectum.
Counted across every colonoscopy
The count adds together polyps from all your colonoscopies, not only the latest one. That is why the diagnosis sometimes arrives on a second or third procedure, after earlier polyps were already removed.
Keep a copy of
- Every colonoscopy report
- Every pathology report on removed polyps
- Any earlier gene test result
Other conditions ruled out
Other polyposis conditions, such as MUTYH-associated polyposis, can look similar. If adenomas are mixed in with the serrated polyps, or bowel cancer runs in the family, a gene test helps rule these out.
Not sure whether this applies to you?
Ask an oncologistAfter the diagnosis
What happens once the syndrome is diagnosed?
Clearing the bowel
The first aim is to remove every significant polyp, which can take more than one colonoscopy. Large or flat polyps may need an endoscopist with specialist experience.
Colonoscopy on a regular rhythm
Once the bowel is cleared, colonoscopy is repeated regularly, usually every year or two, depending on what each procedure finds. Good bowel preparation matters, because flat polyps are easy to miss.
Genetic counselling, where it helps
A counsellor is usually involved when polyps appear young, when bowel cancer runs in the family, or when adenomas are found too. They decide whether a gene panel is worth doing.
Relatives are offered colonoscopy
Brothers, sisters and children are usually offered colonoscopy earlier than the general population. The starting age depends on your family's history.
Surgery, only if needed
If polyps cannot be controlled by colonoscopy, or a cancer is found, removing part of the bowel is discussed as one option among several. Most people never need it.
On your report
The words you will meet, in plain language
- Serrated polyp
- A polyp with a saw-tooth pattern under the microscope. Some types can slowly become cancer if left in place.
- Sessile serrated lesion
- A flat serrated polyp, often on the right side of the bowel, that can be hard to see. Older reports call it a sessile serrated adenoma.
- Hyperplastic polyp
- A common serrated polyp, usually small. On its own it is rarely a worry, but it counts towards the diagnosis.
- Proximal to the rectum
- Anywhere in the large bowel above the rectum. The criteria count the polyps found here separately.
- RNF43
- A gene that helps control growth in the bowel lining. A fault in it explains a small number of families with the syndrome.
- Polyposis
- Having many polyps, rather than the one or two that are common as people get older.
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Side by side
What the diagnosis changes, and what it does not
It does change
It does not change
Colonoscopy becomes regular and lifelong
Under regular colonoscopy, most people never develop bowel cancer
Close relatives are offered earlier colonoscopy
Relatives need no gene test unless a fault is found in you
A gene test may be considered
A normal gene test does not remove the diagnosis
Stopping smoking matters more
Most people need no screening of other organs
Commonly believed
Four things patients assume, and what is actually true
"My gene test was normal, so I do not have the syndrome."
The diagnosis comes from the colonoscopy. Most people with the syndrome have a normal gene test. A normal result means no known single fault was found, not that the polyps are unimportant.
"Hyperplastic polyps are harmless, so they do not count."
A single small one usually is harmless. In this syndrome they are still counted, because the overall pattern matters more than any one polyp.
"It is not in the genes, so my family is fine."
Close relatives still have a higher chance of bowel cancer. They are offered colonoscopy earlier than usual, even though there is no gene to test them for.
"Once the polyps are removed, I am done."
New polyps keep appearing over the years. Regular colonoscopy for life is what keeps the risk low. Skipping checks lets flat polyps grow unseen, and those are the ones that matter most.
Being straight with you
What can this page not tell you?
It cannot tell you whether your own results meet the criteria. That is for your gastroenterologist, working from the reports of every procedure you have had. If a gene test does find something, what your specific variant means is a question for the counsellor who ordered the test.
Where the evidence is thin
The genetics of this syndrome is still being worked out. RNF43 explains only a small share of families, and other suggested genes rest on a handful of reports. Advice for relatives is based on patterns seen in families, not on a gene result, and it may change as studies grow.
Who this does not apply to
Most people with a few serrated or hyperplastic polyps do not have the syndrome. One or two small polyps are very common with age. Gene changes found only inside a bowel tumour belong to treatment planning, covered under targeted therapy.
Families often move between hospitals and districts over the years. Keep every report together, because the diagnosis depends on counting all of them.Questions we are asked
Common questions about serrated polyposis syndrome
Is serrated polyposis syndrome a cancer?
No. It is a condition that raises the chance of bowel cancer, because some serrated polyps can slowly turn into cancer. Removing polyps regularly at colonoscopy keeps that chance low for most people.
Should I have a genetic test?
Sometimes. It is usually offered when polyps appear young, when bowel cancer runs in the family, or when adenomas are found alongside serrated polyps. Most people with the syndrome have a normal result. Your counsellor will tell you whether it is worth doing.
How often will I need a colonoscopy?
Usually every year or two once the bowel has been cleared, depending on how many polyps are found each time. Your gastroenterologist sets the interval and may shorten or stretch it as the pattern becomes clearer.
Should my brothers, sisters and children be checked?
Yes. They are usually offered colonoscopy earlier than the general population, even with no gene fault to test for. The starting age depends on your family's history, and your specialist will advise on timing for each relative.
Does smoking really make a difference?
Yes. Smoking is linked to serrated polyps and to having more of them. Stopping is one of the few changes within your control. Ask your doctor about support to quit, because it is much easier with help than alone.
Will I need surgery?
Most people do not. Surgery is considered when polyps are too many or too large to manage by colonoscopy, or when a cancer is found. If it is suggested, it is discussed as one option among several, with time to decide.
Why was I diagnosed only after several colonoscopies?
Because the count adds up polyps from all your procedures. Earlier ones may have found fewer, or flat polyps may have been hard to see. Once the total meets the criteria, the diagnosis applies from then on.
Where do I start if I think this applies to me?
Gather every colonoscopy and pathology report you have and take them to a gastroenterologist or a genetics clinic. Call the CION helpline if you are unsure who to approach, and someone will point you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- Gut (British Society of Gastroenterology) — Guidelines for the management of hereditary colorectal cancer from the BSG, ACPGBI and UKCGG
- National Cancer Institute — Genetics of Colorectal Cancer (PDQ) - Health Professional Version
- NCCN — Genetic/Familial High-Risk Assessment: Colorectal, Endometrial, and Gastric
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
The rarer polyposis genes: what they doRNF43 and its neighbours, in plain languageThe rarer polyposis genes: which cancers and what riskWhat each gene is known to raise, and where evidence is thinTesting the family for the rarer polyposis genesWho should be checked, with or without a gene resultPolymerase proofreading-associated polyposisAnother rare polyposis condition, for comparison
Talk to us
Has a colonoscopy found many serrated polyps?
Tell us what the colonoscopy and pathology reports say and who else in the family has had polyps or bowel cancer. We will help you work out whether a genetic referral makes sense. One helpline serves every CION centre.