An Overview of Sessile Polyps

This type of polyp may be found in the colon and is flatter in shape

A sessile polyp grows flat on the lining of the large intestine, or colon. It does not have a stalk, like a pedunculated polyp, making it harder to find and remove. A certain type of sessile polyp, called sessile serrated adenoma, is considered precancerous and may be a precursor for up to 30% of all colorectal cancers. Sessile polyps may be found during a colorectal cancer screening and are usually removed during a scheduled surgery or a colonoscopy.

This article explains the different types of sessile polyps and their causes. It also covers the importance of various screening tests in identifying and removing polyps to prevent them from becoming cancerous.

Colon polyp



Polyp Types and Cancer

Sessile polyps are differentiated from pedunculated polyps by their shape, since sessile polyps are flat. When a healthcare provider performs a colonoscopy, using a lighted tube called an endoscope to see in the colon, it may be more challenging to find less visually obvious sessile polyps.

The provider, typically a specialist in digestive diseases called a gastroenterologist, also removes any polyps during the procedure. Apart from sessile polyps, other types of polyps they might identify include:

  • Inflammatory polyps, caused by chronic conditions such as inflammatory bowel disease (IBD)
  • Hyperplastic polyps, a common type that's usually non-cancerous
  • Tubular adenoma, a typically small polyp that can develop into cancer
  • Villous adenoma, a concerning colon polyp found in small finger-like structures called villi

Most people will not know that they have polyps growing in their colon because there are usually no symptoms.

Polyps and Cancer Screening

Colon polyps grow slowly, but because they can grow large over time and become cancerous, it is important to have them removed. Colon polyps can be removed during a colonoscopy. This is why a screening colonoscopy is recommended for people who are at average risk of having colon polyps starting at age 45. Removing a polyp prevents it from becoming cancerous.

Sessile Polyp Types

Sessile polyps, with their flat profile inside the colon, also come in different types. They include:

  • Sessile serrated adenomas: These sessile polyps have a sawtooth pattern when viewed under a microscope. They are considered precancerous, in what is now known as the serrated neoplasia pathway for developing cancer. They need to be removed and you may need surveillance colonoscopies more often if you have them. They're found more often in people who smoke.
  • Villous: This type of polyp carries a high risk of becoming cancerous and is often sessile (rather than pedunculated).
  • Tubular: This type of polyp, which is also the most common, may have a lower risk of becoming cancerous.
  • Tubulovillous: This type of polyp has both tubular and villous growth.

What Percent of Sessile Polyps Are Cancerous?

The answer's not entirely clear. In recent decades, though, researchers have learned that sessile polyps give rise to many more colon cancers than once thought. Part of the reason may be because they're harder to detect and remove, and they often grow in the right-sided colon where they're more difficult to access. That's especially true of sessile serrated adenomas (SSA).


Most people do not know that a sessile polyp may be present in their colon because there aren’t any symptoms. Polyps may not cause any symptoms until they grow larger and/or become cancerous.

Colon polyps that are currently not causing any signs or symptoms may be found during a screening colonoscopy. When polyps are found they are, in most cases, removed to prevent the development of colon cancer.

The lack of symptoms when you have a polyp is one reason why it is important for those who are at risk of developing colon cancer to have regular colon cancer screenings.

When a polyp in the colon does cause signs or symptoms, these may include:

  • Anemia: A polyp that bleeds can cause blood loss, even if the blood loss is not enough at one time to be visible on or in the stool. 
  • Constipation: When polyps grow larger, they can block the inside of the large intestine (the lumen). This can mean that stool isn’t able to pass the area of the polyp growth, which may cause constipation.
  • Change in stool color: When there is a change in stool color that persists beyond a few days and can’t be explained by diet, medication, or supplements, it is a reason to talk to a healthcare provider. Blood in the stool from a polyp that is bleeding can cause stool to appear dark or black.
  • Diarrhea: Diarrhea could be a result of only liquid stool being able to pass the blocked area of the intestine. If symptoms go on for three or more days, speak to medical professional.
  • Pain: Pain is not a common symptom until polyps grow large enough that they start pressing on other areas in the abdomen. At this time there may also be other signs and symptoms of a blockage due to the size of the polyp.
  • Rectal bleeding: Hemorrhoids are a common cause of bleeding from the rectum. Polyps may also lead to rectal bleeding but without pain. A healthcare provider will need to diagnose the cause.


Polyps may grow anywhere within the large intestine. While there are currently no known ways to prevent polyps from growing, there are several known factors that may increase the risk of developing polyps.

Some types of polyps, including sessile serrated polyps, may form because of gene mutations. A mutation could cause certain cells to grow in an uncontrolled way. This could lead to the development of a polyp that continues to grow unchecked.

Some of the risk factors that are known to contribute to the growth of polyps are:

  • Age: Polyps become more common as people get older. While common in people over age 50, they're increasingly seen in younger people.
  • Alcohol: Drinking is associated with an increased risk of developing colon polyps.
  • Inflammation: Digestive conditions, such as Crohn’s disease or ulcerative colitis, can lead to the growth of polyps. Managing digestive disease well is key to limiting inflammation.
  • Ethnicity: There may be an increased risk of developing colon cancer in Black people.
  • Family history: There is an increased risk of polyps in those people whose close family members have had either colon polyps or colon cancer.
  • Sedentary lifestyle: Being less physically active may be associated with an increased risk of developing colon polyps.
  • Smoking: The risk of developing colon polyps may be increased in those who smoke cigarettes.
  • Type 2 diabetes: Those who are diagnosed with Type 2 diabetes and whose disease is not well controlled may have an increased risk of developing colon polyps.
  • Weight: Obesity may be associated with an increased risk of developing colon polyps.


Two broad categories into which colon polyps are usually placed are neoplastic and non-neoplastic. In most cases, non-neoplastic polyps are ones that do not become cancerous. Hamartomatous, hyperplastic, and inflammatory polyps are types of non-neoplastic polyps.

Neoplastic polyps are those that may have an increased risk of becoming cancerous, especially as they grow larger. Not every polyp will develop into cancer, however.

Screening for polyps is the best way to find them before they can grow larger and cause health problems. Regular screening is also advised for those who have a history of an inflammatory digestive condition such as Crohn’s disease or ulcerative colitis.

It’s important for those who are at increased risk of developing colon polyps to work with their healthcare provider to determine when and how to receive screening. Most of the time, if polyps are present, they are found during a screening.

Screening Options for Polyps

Screening options for finding polyps in the colon include:

  • Colonoscopy, to remove polyps and provide tissue samples when biopsy is needed
  • Sigmoidoscopy, a procedure similar to colonoscopy but only in the sigmoid colon
  • Stool tests, which screen for signs of polyps in a stool sample, including blood or genetic DNA
  • Virtual colonoscopy, also known as CT colonography, offers less-invasive imaging of the colon


Sessile polyps are usually removed during colonoscopy. If a sessile polyp cannot be removed, a provider may choose to use surveillance instead, and do another test after a certain interval of time to see if the polyp has changed. This could mean having more frequent colonoscopies. 

Your healthcare provider will advise you on when polyp screening or other tests are necessary. The decision is made on factors that include:

  • The type of polyps that were found
  • How many polyps were found
  • How large your polyps are
  • If any cancerous cells were found on a biopsy

If biopsy results show that a polyp is cancerous, it will need to be removed. If it’s not possible to remove the polyp during a colonoscopy, it may be necessary to have surgery to remove it.

Other treatments may also be needed in order to ensure that all the cancerous material has been removed. After a cancerous or potentially cancerous polyp is removed, the tissue will be sent out for further testing by a pathologist.

Follow-Up Screenings for Polyps

Your healthcare provider will use guidelines to determine when there should be another screening test. One example of a potential colonoscopy follow-up schedule might be:

  • No polyps: 10 years
  • One to two polyps less than 10 millimeters (mm) in size: Seven to 10 years
  • Three to four polyps <10mm: Three to five years
  • More than 10 polyps: Next colonoscopy in one year
  • Advanced polyps: Next colonoscopy in three years

A Word From Verywell

A colonoscopy is considered the best option for finding colon polyps and removing them. Other tests are available and may also be used to screen for polyps, but polypectomy will still be needed in order to prevent the potential for polyps to develop into colon cancer. People who have concerns about their colon cancer risk should speak to a healthcare provider about ways to reduce their risk, including lifestyle changes.

Frequently Asked Questions

  • Are sessile polyps always malignant?

    No. However, polyps that are sessile adenomas have the potential to become malignant, which is why they should be removed. About two-thirds of all colon polyps are adenomas.

  • How common are sessile polyps?

    They're quite common. A study of 27,129 colon polyps that were removed found 43% were flat, or sessile. Fifty-six percent were protruded (pedunculated or elevated polyps) and 1.2% were depressed. The research found an unusually elevated cancer incidence with the depressed polyps.

  • Which types of colon polyps are most likely to turn into cancer?

    Villous adenomas, also called tubulovillous adenomas, and large serrated sessile polyps are either precancerous or carry a high risk of becoming cancerous.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Amber J. Tresca
Amber J. Tresca is a freelance writer and speaker who covers digestive conditions, including IBD. She was diagnosed with ulcerative colitis at age 16.