A colon polyp is a small growth on the inner wall of the large bowel or rectum [2]. Most polyps are small and contain no cancer [4]; but some of them, namely adenomas and sessile serrated polyps, can turn into cancer if they are not removed [1, 2]. Removing these polyps during a colonoscopy helps prevent deaths from bowel cancer [6], and their type, size and number decide when the next colonoscopy is due; for example, 7 to 10 years later after 1 or 2 tubular adenomas smaller than 1 cm [7].
Key points
- Polyps are very common: a doctor who performs colonoscopy well should find an adenoma in at least 1 in 3 people aged 45 or over [9].
- Small polyps almost never contain cancer: in a study of more than 42,000 polyps smaller than 1 cm, none was cancer [4].
- Removing adenomas saves lives: in a large study, deaths from bowel cancer among people who had their adenomas removed were about half the expected number [6].
- The next colonoscopy depends on the pathology result: from 7 to 10 years later after 1 or 2 small adenomas, to 3 years or sooner for larger or more numerous polyps or polyps with high-grade dysplasia [7].
- Your family matters too: if your polyp was advanced and was found before the age of 60, your parents, brothers, sisters and children should have colonoscopies earlier [11].
What is a colon polyp, and what types are there?
A polyp is an extra growth on the inner lining of the large bowel or rectum [2]. Polyps are removed during a colonoscopy and sent to the pathology laboratory; the pathology result tells you what type of polyp it was [7]. The name of each type is given in the table so that you can find it on your report. For the other terms on the report, see: How to read your pathology report
| Type of polyp | What it means | Cancer risk |
|---|---|---|
| Hyperplastic polyp | The most common type of serrated polyp; usually small [2, 5] | Rarely becomes cancer [2] |
| Tubular adenoma | The most common type of adenoma; almost all small adenomas are of this type [4] | Not cancer itself, but it can turn into cancer over time; that is why it is removed [1] |
| Tubulovillous or villous adenoma | An adenoma that is partly or entirely villous (finger-like) under the microscope | Can turn into cancer and counts as an advanced adenoma [7] |
| Sessile serrated lesion or polyp | A flat, broad polyp with saw-toothed edges under the microscope [2] | If it is not removed, it is more likely than a hyperplastic polyp to turn into cancer [2, 5] |
| Traditional serrated adenoma | Another type of serrated polyp, seen less often [5] | If it is not removed, it can turn into cancer [2, 5] |
"Benign" on a pathology report means the polyp is not cancer. After a polyp has been completely removed, follow-up colonoscopies are for finding new polyps [7].
Are colon polyps dangerous?
Most polyps are not dangerous, especially when they are small and have been completely removed [4, 7]. Three things increase the risk [1, 7]:
- Size: a polyp of 1 cm or larger
- Type: tubulovillous or villous adenomas, and sessile serrated polyps
- High-grade dysplasia: cells that look very abnormal under the microscope
An adenoma with any of these features is called an "advanced adenoma" [7]. Such a polyp carries a real risk if it is not removed: researchers in Germany estimated that about 1 in 4 people aged 55 with an advanced adenoma would develop bowel cancer within 10 years, and that this risk rises with age [10]. That is why polyps are removed rather than watched.
Having had high-risk adenomas also raises the risk of bowel cancer in the future; that is what regular follow-up colonoscopy is for [1].
What do low-grade and high-grade dysplasia mean in a colon polyp?
Dysplasia means that some cells look abnormal under the microscope. Dysplasia is not cancer, but it can sometimes turn into cancer. How severe it is depends on how abnormal the cells look [3].
- Low-grade dysplasia: this is what is seen in almost all small adenomas [4]. If the adenoma was small and was completely removed, the risk is low [8].
- High-grade dysplasia: a more serious change that makes the adenoma "advanced", although it is still not cancer [3, 7]. It is rare in small polyps: in one study it was seen in fewer than 1 in 100 small adenomas [4]. If it was completely removed, the next colonoscopy is 3 years later [7, 8].
If your pathology report contains the word "carcinoma" or "cancer", the polyp contained cancer; show the report to your doctor promptly so that they can decide on the next step. Read more: Bowel cancer
How many polyps is normal in a colonoscopy?
Finding one or more polyps is very common and does not mean you have cancer:
- A doctor who performs colonoscopy well finds at least one adenoma in more than 1 in 3 people aged 45 or over; more often in men than in women [9].
- Serrated polyps are found in 2 to 4 in 10 people at average risk, and most of them are hyperplastic [5].
- After 1 or 2 small adenomas have been removed, the chance of finding an advanced polyp at the next colonoscopy is low, and almost the same as for someone whose colonoscopy was normal [7].
- The more adenomas there are, the sooner the next colonoscopy. If more than 10 adenomas have been found in total, your doctor may suggest genetic testing [7].
When should I repeat colonoscopy: every 5 or 10 years?
When your next colonoscopy is due depends on the pathology result. This table is based on the guideline of the joint task force of the US gastroenterology societies, and it applies when the colonoscopy was complete and of high quality and all polyps were completely removed [7]. Your doctor may change the interval because of your family history or other circumstances.
| What was found at colonoscopy | Next colonoscopy |
|---|---|
| Normal colonoscopy, no polyps | 10 years later [7] |
| Hyperplastic polyp smaller than 1 cm | 10 years later [7] |
| 1 or 2 tubular adenomas smaller than 1 cm | 7 to 10 years later [7] |
| 1 or 2 sessile serrated polyps smaller than 1 cm | 5 to 10 years later [7] |
| 3 or 4 adenomas smaller than 1 cm | 3 to 5 years later [7] |
| 5 to 10 small adenomas, an adenoma of 1 cm or larger, a tubulovillous or villous adenoma, or high-grade dysplasia | 3 years later [7] |
| A sessile serrated polyp of 1 cm or larger or with dysplasia, or a traditional serrated adenoma | 3 years later [7] |
| More than 10 adenomas | 1 year later; and possibly genetic testing [7] |
| A polyp of 2 cm or larger removed in pieces | 6 months later, to make sure it was removed completely [7] |
The European guideline does not consider a separate follow-up colonoscopy necessary after 1 to 4 small adenomas with low-grade dysplasia; where no regular screening programme is available, colonoscopy is repeated after 10 years [8].
What are the benefits and risks of removing a polyp?
Most polyps are removed during the colonoscopy itself [1]. In a large study in the United States, 2,602 people who had their adenomas removed were followed for up to 23 years. Deaths from bowel cancer among them were about half the number expected in the general population [6].
The US National Cancer Institute says that removing polyps larger than 1 cm may lower the risk of bowel cancer, but it is not known whether removing smaller polyps lowers the risk. The risks of removing polyps are bleeding and a tear in the bowel wall [1].
If I had polyps, what should my family do?
If your polyp was an "advanced adenoma" (1 cm or larger, villous, or with high-grade dysplasia), this matters for your first-degree relatives (parents, brothers, sisters and children) [11]:
- If you were younger than 60 when it was found, or two first-degree relatives have had such a polyp or bowel cancer: they should have a colonoscopy every 5 years, starting at 40 or 10 years before your age at diagnosis, whichever is earlier.
- If you were 60 or older: they can start usual screening at 40.
These recommendations are for advanced adenomas; small, low-risk polyps usually do not change your relatives' screening plan [11]. Read more: At what age is a screening colonoscopy needed? and Is cancer hereditary?
When should I call my doctor?
- After a polyp has been removed: if you have heavy bleeding from the back passage, severe or worsening tummy pain, or a fever, seek care straight away; bleeding and a tear in the bowel are risks of polyp removal [1]. If it is severe, call your local emergency number.
- Get your pathology result: the timing of your next colonoscopy cannot be decided without it [7].
- Do not put off your follow-up colonoscopy, especially if you have had an advanced adenoma or many polyps [7].
- If blood in your stool, a change in bowel habit or unexplained weight loss appears before your next colonoscopy is due, do not wait. Read: Blood in your stool: piles or bowel cancer?
Frequently asked questions
My pathology report says "benign". Does that mean I have nothing to worry about?
I have a hyperplastic polyp. When should I repeat colonoscopy?
What is the cancer risk of a sessile serrated polyp?
These polyps can turn into cancer through a separate pathway and carry more risk than hyperplastic polyps [2, 5]. People who have one are more likely to have an advanced polyp at the same time or later [5]. That is why the interval to the next colonoscopy is shorter: from 5 to 10 years for 1 or 2 small polyps, to 3 years for a large polyp or one with dysplasia [7].
Can a polyp come back after it has been removed?
Does a polyp in the large bowel always need to be removed?
Can a stool test replace colonoscopy after polyps?
For someone who has had an advanced adenoma or several adenomas, guidelines recommend follow-up colonoscopy [7, 8]. But the European guideline says that someone who has had only 1 to 4 small adenomas with low-grade dysplasia can return to usual screening, which may be a stool test [8]. Read about screening methods: At what age is a screening colonoscopy needed?
Post-polypectomy surveillance intervals and evidence (for doctors)
For physicians
USMSTF 2020 (Gupta et al.). All recommendations assume a high-quality colonoscopy (caecal intubation, bowel preparation adequate to detect polyps larger than 5 mm, adequate ADR and complete polyp resection). Normal: 10 years. 1–2 tubular adenomas <10 mm: 7–10 years (strong recommendation, moderate-quality evidence); the rate of metachronous advanced neoplasia in this group is no more than 2% higher than after a normal colonoscopy. 3–4 adenomas <10 mm: 3–5 years. 5–10 adenomas <10 mm, an adenoma ≥10 mm, tubulovillous/villous histology or high-grade dysplasia: 3 years. More than 10 adenomas: 1 year, and genetic evaluation based on cumulative adenoma number, age and family history. Piecemeal resection of an adenoma ≥20 mm: 6 months. Serrated: up to 20 hyperplastic polyps <10 mm (rectosigmoid or proximal): 10 years; 1–2 SSPs <10 mm: 5–10 years; 3–4: 3–5 years; 5–10: 3 years; SSP ≥10 mm or with dysplasia, and TSA: 3 years; HP ≥10 mm: 3–5 years; piecemeal resection of an SSP ≥20 mm: 6 months [7].
ESGE 2020 (Hassan et al.). Complete removal of 1–4 adenomas <10 mm with low-grade dysplasia, irrespective of villous component, or of any serrated polyp <10 mm without dysplasia: no endoscopic surveillance and return to screening, and colonoscopy 10 years later where organised screening is not available (strong recommendation, moderate-quality evidence). At least 1 adenoma ≥10 mm or with high-grade dysplasia, ≥5 adenomas, or any serrated polyp ≥10 mm or with dysplasia: 3 years. Piecemeal resection ≥20 mm: 3–6 months, then 12 months later. If the first surveillance shows no polyps requiring surveillance: a second one after 5 years, then return to screening [8].
Supporting evidence. In the Ponugoti et al. database, there was no cancer among 42,630 polyps <10 mm (36,107 polyps ≤5 mm and 6,523 polyps 6–9 mm); high-grade dysplasia was present in 0.3% of adenomas ≤5 mm and 0.8% of adenomas 6–9 mm, and advanced histology in 2.1% and 5.6%; 22,952 of 23,524 small adenomas were tubular [4]. In the National Polyp Study (2,602 patients with adenomas removed, median follow-up 15.8 years), 12 CRC deaths occurred against 25.4 expected; standardised incidence-based mortality ratio 0.47 (95% CI 0.26 to 0.80), i.e. a 53% reduction [6]. Brenner et al.'s estimate from 840,149 screening colonoscopies in Germany: annual transition rate from advanced adenoma to CRC rising from 2.6% at 55–59 years to 5.6% (women) and 5.1% (men) at 80 years and older; 10-year cumulative risk from 25.4% (women) and 25.2% (men) at 55 years to 42.9% and 39.7% at 80 years [10]. The prevalence of serrated polyps in average-risk individuals is 20–40%, most of them hyperplastic; SSLs are found in up to 15% of individuals by high-detecting endoscopists, and SSLs and TSAs are CRC precursors [5]. ADR performance target in the 2024 ACG/ASGE quality indicator update: ≥35% in patients aged 45 and over (40% in men, 30% in women) [9].
Relatives. CRC or a documented advanced adenoma in one first-degree relative younger than 60, or in two first-degree relatives at any age: colonoscopy every 5 years from age 40 or 10 years before the age at diagnosis of the youngest affected relative (whichever is earlier); one first-degree relative aged 60 or over: average-risk screening options from age 40 [11].
Scientific evidence
Scientific evidence
1 itemColorectal Cancer Screening: Recommendations for Physicians and Patients From the U.S. Multi-Society Task Force on Colorectal Cancer
Related cancer types
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References
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