Colon Polyps

Colorectal cancer almost always begins as a polyp that transitions into cancer over time.

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In most cases, polyps take years to grow into cancers. If you have/had a colon polyp, here’s what you need to know.

What is a colon polyp?

A polyp is a small outgrowth of cells or tissue that occurs in the lining of the colon or rectum. Picture a pimple, but inside your colon or rectum. There are a few different types of polyps, and we know now that colorectal cancers begin as polyps.

Only a very small percentage of polyps and only certain types of polyps can become cancerous. Most polyps and early-stage colorectal cancers do not cause symptoms that you can see or feel.

Polyp symptoms

Most of the time, polyps don’t have symptoms. However, for some people, polyps bleed, causing red or black blood in the stool. Bleeding may be intermittent. It is always important to notify your doctor if you see blood in your stool.

Colon polyp shapes

Pedunculated Polyps

Some polyps grow on the end of a stalk and look similar to a mushroom. These are called pedunculated polyps.

Sessile (or Flat) Polyps

Sessile polyps grow without the narrow stalk and lie flat against the wall of the colon. These are also known as flat polyps. They are plate-shaped and are very common in the colon and rectum. Since their shape makes them harder to see, they may be more likely to be missed compared to other types of polyps that grow on a small stalk.

Pedunculated, sessile, and flat polyps can be benign (noncancerous), precancerous, or cancerous.

Cancerous and Precancerous Polyps

Just because you have a colon polyp, that doesn’t mean it’s cancer (also called a malignant tumor). Few polyps grow into cancer. Cancer risk is determined by how a polyp appears under a microscope.

Advanced adenomas, sessile serrated polyps (also known as sessile serrated adenomas), and traditional serrated adenomas have the highest risk of becoming cancerous.

On the other hand, hyperplastic, inflammatory, and hamartomatous polyps are unlikely to become cancer.

Knowing whether you have had an advanced adenoma, sessile serrated polyp/adenoma, or traditional serrated adenoma is important to know your cancer risk. It’s important to ask your doctors any questions you have about your pathology report.

Polyp Types

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. Most likely, inflammatory and hamartomatous polyps won’t become cancer. Adenomas, hyperplastic, and serrated come with a cancer risk. It’s important to ask your doctors any questions about your pathology report.


Adenomatous Polyps (Adenomas)

These are one of the most common polyp types, and adenomas are also the most common polyp type to cause colorectal cancer. However, only a small fraction of adenomas will become colorectal cancers. Adenomas are described by growth patterns, or microscopic descriptions, that a pathologist makes by examining the removed polyp under a microscope after the colonoscopy. The main types are:

  • Tubular growth pattern – generally applies to smaller adenomas growing in a tube shape, less than half an inch in size
  • Villous adenoma – generally applies to larger adenomas growing in a shaggy, cauliflower-like shape
  • Tubulovillous – adenoma with a mixture of both tubular and villous growth patterns

When an adenoma is over 1 centimeter or has tubular, villous, or tubullovillous features, it is called an “advanced adenoma.” Advanced adenomas are associated with elevated risk of colorectal cancer. Therefore, it’s important to detect these polyps via screening and remove them via colonoscopy so cancer can be prevented.

If you’ve had an adenoma in the past, you are more likely to develop new adenomas in the future, which is why the number and size of adenomas helps determine how often you will need to repeat a colonoscopy.

It’s also very important to tell your immediate biological family members (parents, siblings, children) if you’ve had adenomatous polyps, as they are more likely to have adenomas and may need to start screening and screen more frequently.

Hyperplastic Polyps

Although common, they are not likely to become colorectal cancer over time unless caused by a hereditary (family-linked) condition.

Sessile-Serrated and Traditional-Serrated Polyps

These polyps have an appearance of a “saw tooth” border under the microscope and, in some cases, do progress to colorectal cancer. They are less common than adenomas.

Hamartomatous Polyps

Generally, these are noncancerous unless associated with a hereditary syndrome like Peutz-Jeghers, Cowden, or Juvenile polyposis (JPS). These polyps are very rare.

Inflammatory Polyps

These are also rare and can be seen in chronic diseases in the colon or rectum, like ulcerative colitis or Crohn’s disease. They do not typically transform into colorectal cancer.

What is dysplasia?

Dysplasia describes how histologically advanced (how developed the polyp appears when viewed under a microscope) your polyp is. All adenomas are dysplastic. Pathologists use the term “high-grade dysplasia” to distinguish polyps with more advanced histology–those that appear to be cancer.


How do I know if I have colorectal polyps?

There are many screening methods that can detect precancerous polyps:

  • Colonoscopy
  • Flexible sigmoidoscopy
  • CT colonography (virtual colonoscopy)
  • Stool DNA test (Cologuard®)
  • Fecal immunochemical test (FIT)
  • High-sensitivity guaiac fecal occult blood testing (FOBT)

All methods can detect polyps and cancers to varying degrees. The benefits of some of the stool-based tests are that they are noninvasive tests and can be performed at home. But they must be done more frequently (every one to three years) to detect colorectal cancers. They are less sensitive in detecting polyps than colonoscopy.

The more invasive, direct visualization techniques (colonoscopy, CT colonography, flexible sigmoidoscopy) allow doctors to see polyps. These screening tests can be done less frequently. Colonoscopy and flexible sigmoidoscopy allow for the identification and removal of polyps.

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

The general theory is that it takes about 10 years for an adenoma to turn into cancer. However, this transition can take longer or shorter. In individuals with a hereditary syndrome (where polyps and cancer develop at an earlier age), the transition may be much faster.

How many colorectal polyps is a lot?

With some types of hereditary syndromes, which lead to an increased risk of colorectal cancer, a person may have 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 all polyps removed to prevent cancer.

It is important to know the type and number of polyps your doctor found so this information can be relayed to your first-degree biological relatives. Your personal history of high-risk polyps could impact their cancer risk and when they need to start screening.

What if polyps are found during a colonoscopy?

If you underwent a colonoscopy, your doctor likely performed a polypectomy and removed your polyp(s) as your large intestine was examined. Most patients go under sedation when this happens and don’t feel pain during the polyp removal or afterward. If a doctor performed a polypectomy, you will need to follow up to find out what type of polyps they removed.

  • Polyp completely 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 tissue to the pathology laboratory to determine the histology.
  • Polyp too large to grasp and remove during a colonoscopy? Although rare, a follow-up colonoscopy or surgery may be required.

Removing the colon polyp can stop the transition to colorectal cancer if it’s done early enough. This is why colorectal cancer screening is so important and why colorectal cancer is considered a preventable disease. After a colonoscopy, the timing of the next colonoscopy depends on the findings.

If the exam was complete and you do not have any polyps, you will not likely need another colonoscopy for 10 years.

However, if you have one large or many small adenomas, you will be asked to return for a repeat colonoscopy (surveillance colonoscopy) sooner—perhaps in three or five years. These follow-up colonoscopies allow for the detection and removal of new polyps that may have grown.

Your follow up will depend on:

  • The size of polyp(s)
  • How many polyps are found
  • The type of polyp(s)
  • Your family and personal history

Don’t be surprised if your doctor recommends that you need to be screened every three to five years if polyps were found.

The good news: Polyps don’t come back once removed.

What if I have a cancerous colon polyp?

If you were diagnosed with a cancerous colon polyp, you were diagnosed with colorectal cancer. We are here for you. You will need to schedule recommended follow-ups and talk to your doctor about who to include on your treatment team.

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

It is always a good idea to seek a second opinion at any time. Need help finding a doctor? Use our Provider Finder.

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 learn if you have a family history of colon cancer or rectal cancer.

Studies suggest first-degree biological relatives of patients with advanced adenomas and/or advanced serrated polyps face increased risk for colorectal cancer, and they need to discuss starting screening at a younger age and screening more frequently with their health care provider.

Additionally, people with Lynch syndrome or familial adenomatous polyposis (FAP) face a high risk for developing polyps.

Are certain populations more susceptible to developing advanced adenomas?

Advanced adenomas occur in men and women of all socio-demographic backgrounds, but they are more frequent with advancing age and among Black individuals.

Patients with a family history of advanced adenomas, or those who have personally had advanced adenomas, are also more likely to develop them in the future.

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Medical Review

Folasade P. May, MD, PhD, MPhil


Last Reviewed: December 13, 2023