Colorectal cancer often takes many years to grow, and nearly all cases of colon cancer and rectal cancer start off as a polyp. Here’s everything you need to know about colon polyps and rectal polyps:

What are colorectal polyps?

A polyp is a group of cells that grow together, and a colon polyp occurs when these cells grow on the inside of the colon or rectum. There are a few different shapes of polyps.

Pedunculated polyps

Some polyps grow on the end of a stalk and look similar to a mushroom (this is called a pedunculated polyp). Adenomas are polyps that grow like a mushroom with a stalk.

Sessile (or flat) polyps

Sessile polyps grow without the narrow stalk and seem to lie flat against the wall of the colon. These polyps are also known as flat polyps. Sessile only means that they don’t have a narrow stalk. It’s possible for a large, protruding polyp to have a sessile base.

Cancerous and precancerous polyps

Both pedunculated and sessile polyps can turn into benign (non-cancerous), precancerous and cancerous polyps. It’s important to know your polyp type – such as hyperplastic, inflammatory, hamartomatous, adenomatous, hyperplastic and sessile serrated polyps – to know your cancer risk.

Keep reading to learn about your risks with these types of colon polyps!

Colon Polyp and Rectal Polyp symptoms

It’s hard to know if you have polyps because they don’t usually cause symptoms until they develop into cancer. This is why screening is important!

Screening for colorectal cancer = screening for polyps.

Most polyps can be safely removed during a colonoscopy, thus removing the risk of the polyp growing into cancer.

Can colorectal polyps bleed?

Most of the time, polyps don’t come with any symptoms. However, for some, polyps bleed. Bleeding may be intermittent. It is always important to notify your doctor if you notice blood in your stool.

Talk to your doctor if you experience rectal bleeding, a change in bowel habits, pain, and anemia. This could mean you have a polyp and you need to be screened, or that you need additional surveillance. Learn more about the symptoms of colorectal cancer.

colon polyp size and type adenoma polyp

Types of colon polyps and cancer risks

Just because you have a polyp, that doesn’t mean it’s cancer (also called a malignant tumor).

Some polyps grow into cancer, but others may not.

Does the size of polyp impact cancer risk?

Your cancer risk does increase with the size of the colon polyp, but there is no specific, generalized size that indicates a polyp is becoming cancerous.

However, 1 centimeter is the cutoff between an “advanced” and “non-advanced” polyp.

If you grow an advanced polyp, your doctor will likely ask you to return for a follow up sooner than normal. Not all polyps will become cancerous, but it is important to remove them all to block the possibility.

What types of colon polyps probably won’t become cancer?

Most likely, these polyp types won’t become cancer.

Inflammatory polyps

These colon polyps are often seen with ulcerative colitis or Crohn’s disease, inflammatory bowel diseases (IBD). Although the polyps are generally non-cancerous, if you have IBD, you are at increased risk of colorectal cancer.

Hamartomatous polyps

Hamartomatous polyps are generally noncancerous, unless they are found in people with a polyposis syndrome like Peutz Jaeghers, Cowden’s, or Juvinille Polyposis, in which case they are associated with the development of colorectal cancer. Learn more about genetic syndromes.

What types of polyps likely become cancer?

These types of polyps come with a cancer risk.

Adenomatous polyps (adenomas)

These polyps are a big deal! Approximately two-thirds of colon polyps are adenomas – that means 66 percent of all colon polyps are precancerous!

Adenomas are described by growth patterns, or microscopic descriptions a pathologist makes to determine how often you need to return for a colonoscopy.

  • Tubular growth pattern – adenomas less than ½ inch
  • Villous growth pattern – describe larger adenomas
  • Tubularvillous – adenoma with a mixture of both tubular and villous growth patterns

If you’ve had an adenoma in the past, you are likely to develop new polyps, and you may need to be screened more often.

Also, if you have adenomatous polyps, it’s very important to tell your family. You may need to be screened sooner.

Keep reading and we’ll explain the hereditary factor of polyps.

Hyperplastic polyps

If a hyperplastic polyp is found on the right side of your colon, some research suggests the polyp could become cancerous. However, if not linked to a hereditary syndrome, hyperplastic polyps generally do not carry a cancer risk.

Sessile-serrated and traditional serrated polyps

Histologically, these polyps appear with a “saw-tooth” (serrated) border of their glands, and they are considered precancerous polyps.

How long does it take a polyp to turn into cancer?

The general theory:  it takes about 10 years for an adenoma (precancerous polyp) to turn into cancer.

This varies for those with a hereditary syndrome – people who often see polyps and cancer at an earlier age.

What is dysplasia?

Dysplasia describes how histologically advanced your polyp is, and all adenomas are dysplastic. Pathologists use the term “high-grade dysplasia” to distinguish polyps with more advanced histology – or polyps that appear more worrisome for cancer.

Colorectal polyps causes

Anyone can grow a polyp, and colon polyps are common. Can you do anything to prevent polyps?

Yes and no.

Your risk of developing a polyp increases with age, which you cannot control. Personal or family history of polyps or colorectal cancer? Your risk is also increased.

However, your risk of colon polyps also goes up:

  • if you smoke
  • If you are are overweight

It’s important to follow a healthy lifestyle to reduce your risk of polyps and cancer. Learn more about colorectal cancer risk factors.

How do I know if I have polyps in my colon and rectum?

Two procedures, colonoscopy and CT colonography, let doctors view your entire colon and look for polyps.


Colonoscopy can detect colon polyps. If your doctor finds a polyp during your colonoscopy, it will most often either get removed immediately or biopsied (if it cannot be fully removed).

Keep reading to learn what to do if you underwent colon polyp removal.

CT Colonography

CT colonography also offers a visualization of your colon and lets your doctor look for polyps. If any polyps are detected during a CT colonography, a follow-up colonoscopy will be scheduled so the doctor can remove the polyp.

FIT-DNA for At Home Screening

While screening tests like FIT-DNA and FIT don’t actually “see” polyps, test results can point health care providers to a need for additional testing.

Do colon polyps and rectal polyps show on CT scan?

A CT colonography is a type of CT scan, and this is the only CT screening option that will detect colon polyps.

Learn more about colorectal cancer screening.

How many colorectal polyps is a lot?

Some types of hereditary syndromes, which lead to an increased risk of colorectal cancer, could leave a person with hundreds of polyps. For others without a genetic link, just one or a few may grow. No matter the number, it is important to have the polyp(s) removed to prevent cancer.

It is important to know how many polyps your doctor found – and to relay that information to your first-degree relatives!

Your polyps could impact their cancer risk and when they need to be screened.


Had colonoscopy, found polyps

When it comes to colon polyps, you’re better safe than sorry.

It’s best to get all polyps removed so you eliminate the chance a polyp turns into cancer.

If underwent a colonoscopy, your doctor likely performed a “polypectomy” and removed your polyp(s). Does it hurt? Not generally, most patients go under sedation when this happens and don’t feel pain during the polyp removal, or after.

  • Polyp removed? The entire polyp will be sent to a pathology laboratory for histology.
  • Polyp cannot be entirely removed? It will typically get biopsied during the colonoscopy, and your doctor will send the biopsy to the pathology laboratory to determine the histology.
  • Polyp too large to grasp and snip off during a colonoscopy? Although rare, a follow up surgery may be required.

Removing the colon polyp can stop the growth of colorectal cancer – if it’s done early enough!

This is why colorectal cancer screening is so important, and why it’s considered to be a preventable disease!

What if I had colorectal polyps removal?

If a doctor performed a polypectomy, you will need to follow up to find out what type of polyps he/she removed.

The type of polyp your pathologist describes in the lab report will determine what comes next.For example, if you had small, hyperplastic polyps, you may not need to do anything more than get a colonoscopy every 10 years (a.k.a., follow screening for the average-risk adult).

But, if you have precancerous polyps/adenomas, you will likely need more regular follow up.The good news:  polyps don’t come back once removed.

However, after polyp removal, your risk of developing new polyps is high – about 5 to 10 percent per year for the first several years!

Your follow up will depend on:

  • the size of polyp(s)
  • how many polyp(s) are found
  • the type of polyp(s)
  • where the polyp(s) are located in the colon
  • your family and personal history

Don’t be surprised if your doctor recommends you need screened 3 to 5 years after your initial polyp removal.

Are polyps hereditary?

Some people carry a hereditary predisposition to colorectal cancer and polyps. That’s why it is important to talk to your first-degree relatives and discuss if anyone’s doctors found and removed polyps during a routine colonoscopy.

Studies suggest first-degree relatives of patients with advanced adenomas and/or advanced serrated polyps face increased risk for colorectal cancer, and need to discuss screening sooner with their health care provider.

If your first-degree relative had a polyp,  it is important to know what type (advanced adenoma or other advanced polyp).Screening options for someone with a family member with precancerous polyps may match those similar to people with family members with a first-degree relative diagnosed with colorectal cancer, which would be at age 40, or 10 years before the age of a colorectal cancer diagnosis in the youngest-affected relative).

Additionally, people with Lynch syndrome or familial adenomatous polyposis face a high risk for developing polyps.Learn more about this in our Genetics Mini Magazine and our Hereditary Colorectal Cancer webinar.

What if I have a cancerous polyp?

If the biopsy of your polyp is positive for colorectal cancer, we are here for you. You will need to schedule recommended follow ups and talk to your health care provider about who to include on a treatment team.

If doctors find cancer, you can rest assured there are resources to help you with a variety of things including making treatment decisions, understanding terminology, working through anxiety and fear, and more.

There are even resources for your loved ones.

It is always a good idea to seek a second opinion at any time.

Resources on Colon Polyps and Rectal Polyps

American Cancer Society: Understanding your pathology report

US National Library of Medicine National Institutes of Health: Sessile Serrated Polyps: Detection, Eradication, and Prevention of the Evil Twin

The American Society of Colon and Rectal Surgeons: Polyps of the colon and rectum

American College of Gastroenterology: Colon Polyps

The AGA Institute: Family History of Colorectal Adenomas 

Fight CRC: Colorectal Cancer Screening Mini Magazine

Fight CRC: Polyps and Prevention Webinar

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Medical Reviewer

Dr. Dennis Ahnen University of Colorado School of Medicine Director of Genetics Clinic, Gastroenterology of the Rockies