An Overview of Sessile Polyps

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

A growth on the lining of the large intestine (also known as the colon) is called a colon polyp. Not all polyps are the same; there are several different types (inflammatory, hyperplastic, adenomatous, and villous) and two shapes, sessile and pedunculated.

A sessile polyp is one that is flat and does not have a stalk. For this reason, sessile polyps can be more challenging to find and remove during a colonoscopy, which is a procedure that looks at the inside of the colon. A pedunculated polyp is one that has a stalk and looks more like a mushroom.

Colon polyps are thought to be the precursor to colon cancer. Most people will not know that they have polyps growing in their colon because there are usually no symptoms. However, it is common for people over the age of 40 years to have polyps in their colon. By age 60, about half of all adults have polyps in their colon.

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 to 50 years. Removing a polyp prevents it from becoming cancerous.

Anatomy of the Large Intestine

The colon is part of the digestive system. It is positioned in the abdomen below the stomach and resembles a tube (because it has an opening on the inside that’s called the lumen). It is shaped like a “U,” meaning that it runs from up one side of the abdomen, across, and down the other side. For an average adult, the colon is about 6 feet long.

Sometimes “colon” and “large intestine” are used interchangeably, but the colon is really one part of the large intestine. Besides the colon, the large intestine also includes the cecum, rectum, and anus.

For the purposes of talking about the parts of the large intestine more easily and precisely, it is divided into different sections. Food moves from the small intestine into the cecum, then the ascending colon, transverse colon, descending colon, sigmoid colon, and finally the rectum. The cecum is located between the end of the small intestine and the start of the large intestine.

The ascending colon is located on the right side of the abdomen, the transverse colon is located in the upper abdomen, and the descending colon is on the left side of the abdomen. The last section of the colon, which is located above the pelvis and has a curve to it, is the sigmoid colon.

The rectum is the part of the small intestine where stool is held until it is time to go to the bathroom. The anal canal is the last section, which is between the rectum and the anus. Stool moves through the anal canal and out of the body through the anus.

Sessile Polyp Types

The different types of polyps, which may be flatter (sessile) in shape include:

  • Sessile serrated. This type of sessile polyp arises from abnormal growth and may be different from other types of polyps. This type of polyp is put in the neoplastic category and is treated as being precancerous. The cells from this type of polyp look serrated or have a sawtooth look under a microscope, which gives them their name. When large sessile serrated polyps are found, it may be necessary to have surveillance colonoscopies or other tests more frequently. This type of polyp is 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 grown.


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: Stool changes color for a variety of reasons and can be entirely normal, especially if it is due to foods or supplements. However, 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 doctor. Blood in the stool from a polyp that is bleeding can cause stool to appear dark or black. When the stool also has a tarry appearance or consistency, that is also a sign that a doctor should be consulted because this change could be from blood.
  • Diarrhea: Diarrhea could be a result of only liquid stool being able to pass the blocked area of the intestine. Most people have constipation or diarrhea from time to time and it goes away on its own, but when these symptoms go on for three or more days it’s a good idea to talk to a physician to see if there’s a reason to look further.
  • 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. However, any bleeding from the rectum should not automatically be assumed to be from a hemorrhoid unless that is confirmed by a physician. This is because a polyp may also bleed and cause blood to appear on the toilet paper and on or in the stool. The most common sign of a polyp is bleeding from the rectum that does not cause any pain.


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.

There’s no way to identify the particular reason(s) why a polyp started to grow in the large intestine. However, some of the risk factors that are known to contribute to the growth of polyps are:

  • Age: One risk factor that can’t be modified is age. Polyps become more common as people get older, and are especially more common in people who are over the age of 50 years.
  • Alcohol: Drinking alcoholic beverages is associated with an increased risk of developing colon polyps.
  • Inflammation: Having inflammation present in the colon as a result of a digestive condition, such as inflammatory bowel disease (Crohn’s disease or ulcerative colitis) is another cause of the growth of polyps. This is why it is important to keep digestive disease well managed to avoid inflammation.
  • Ethnicity: Another risk factor for colon polyps that can’t be changed is heritage. There may be an increased risk of developing colon cancer in people who are of African-American descent.
  • 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: Having 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 which do not become cancerous. Hamartomatous, hyperplastic, and inflammatory polyps are types of non-neoplastic polyps.

Neoplastic polyps are those which 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. Tests to look for colon polyps that are done at regular intervals are recommended for those who have reached the age of 45 to 50 years or for those who are at increased risk because of family history or personal history of colon cancer or colon polyps. 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 physician to determine when and how to receive screening. Most of the time, if polyps are present, they are found during a screening.

Polyps can be removed during some tests, such as colonoscopy, and which eliminates the risk of them growing and developing into cancer. 

Screening options for finding polyps in the colon include:


A colonoscopy is a test that is used to look inside the colon using a long, flexible tube with a camera on the end which is inserted through the anus. During this test, a gastroenterologist (a doctor that specializes in the digestive tract) can see the lining of the colon. If any polyps are present, they can be found and usually are also removed. In addition, biopsies (small pieces of colon tissue) can be taken and sent for testing. Patients are normally sedated during this test. Biopsies can demonstrate if there are any changes in the cell of the colon tissue that might indicate a precancerous condition.


A sigmoidoscopy is similar to a colonoscopy in that it is a test that is used to look inside the colon. It is also conducted using a long, flexible tube that is inserted into the body through the anus. During this test, only the last part of the colon can be seen, which is the sigmoid colon. If any polyps are found they may also be removed. However, only the sigmoid colon can be seen, and polyps visible in any other area of the colon would not be seen or removed. This means that this test has limited use in screening the colon for polyps that may be located in other parts of the colon.

Stool Tests

Screening stool for signs of polyps, including blood, may also be used. With this test, stool samples are collected in a sterile cup either at a healthcare provider’s office or at home, and are taken to a lab for testing. Blood in the stool which can not be seen with the naked eye, which is called occult blood, can be detected upon testing in a laboratory. Blood that appears in the stool could be coming from a bleeding polyp. Another type of stool test looks for DNA, or genetic material, from a polyp or from colon cancer. If blood or genetic material is found in the stool, other tests might be needed to find the cause and to remove it or treat it.

Virtual Colonoscopy

This imaging test, which is also known as a CT colonography, is used to look at the inside of the colon. This is a less invasive test because it is done by taking images. To complete this test, a tube is inserted about 2 inches into the rectum. Patients lie on a table that moves into a CT scanner so that images may be taken.


Sessile polyps are flatter and don’t have a stalk, which, in some cases, may make them more difficult to remove during a colonoscopy. In most cases, however, efforts will be made to remove polyps when they are found. If a sessile polyp can not be removed, a physician 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. 

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.


After a polyp is found and removed, it will be necessary to have more follow-up with a physician to ensure the polyp and/or cancerous material is gone. The doctor will advise on when it will be necessary to do another test to continue to screen for more polyps. The testing schedule will be based on several factors including the type of polyps that were found, how many there were, how large they were, and if any cancerous cells were found on a biopsy.

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

  • Patient has no polyps: Next colonoscopy in 10 years
  • Patient has one to two polyps <10mm: Next colonoscopy in seven to 10 years (instead of five to 10 years)
  • Patient has three to four polyps <10mm: Next colonoscopy in three to five years (instead of three years)
  • Patient has more than 10 polyps: Next colonoscopy in one year (instead of three years)
  • Patient has advanced polyps: Next colonoscopy in three years

A Word From Verywell

Polyps are common in people over the age of 50. It’s important to live a healthy lifestyle to avoid medical problems and reduce the risk of developing polyps, but there are some risk factors that can’t be changed. In many cases, a colonoscopy is considered to be 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.

After polyps are found and removed, it is necessary to continue screening for polyps at whatever interval that is determined by a physician. People who have concerns about their risk of developing colon cancer should speak to a physician about screening methods and how to reduce risk. 

Frequently Asked Questions

  • Are sessile polyps always malignant?

    No. Some are adenomas, which means they're non-cancerous. However, adenomatous sessile polyps 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?

    Around 85% of colon polyps are sessile polyps. Only 13% are pedunculated and 2% are flat.

  • Is a 5-millimeter sessile polyp regarded as large?

    No. Most 5-millimeter (mm) polyps are regarded as quite small. Polyps are considered large when they reach around 20 mm—about as big as an average thumb. There's a 10% chance a colon polyp that size contains cancerous cells.

  • 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.

  • What are complex colon polyps?

    Also known as difficult or defiant polyps, these cannot be easily removed and, if they are, carry a high risk of complications such as bleeding or puncturing the colon. Examples include sessile or pendiculated polyps larger than 2 centimeters and those that are hard to reach or that are wrapped around a fold of colon tissue.

  • How are sessile polyps treated?

    Most are resected (removed) in a procedure called a polypectomy to prevent them from progressing to cancer.

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