An Overview of Sessile Polyps

A sessile polyp is a flat, abnormal tissue growth on the lining of the large intestine (colon). Most sessile polyps are benign, non-neoplastic growths and unlikely to be malignant (cancerous).

However, neoplastic sessile serrated adenomas are precancerous polyps that account for up to 30% of all colorectal cancers. Precancerous colon polyps are common and affect up to 40% of Americans over 50.

Sessile polyps do not typically have symptoms and are often found and removed during a colorectal cancer screening or colonoscopy. However, since sessile polyps are flat or dome-shaped, they can be harder to detect and remove than other types of polyps.

This article discusses sessile polyps. It explains different types of sessile polyps and their related cancer risks. It also covers the importance of colon cancer screenings to identify and remove colon polyps and prevent cancer.

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What Is a Sessile Polyp?

A sessile polyp is a piece of abnormal tissue that grows on the mucosa (tissue lining) of hollow organs.

The term "sessile" means attached directly to the tissue by a broad base. Unlike pedunculated polyps, which are connected by a stalk, sessile growths are flat or dome-shaped and immobile.

While sessile polyps can grow in the bladder, stomach, or uterus, they most commonly occur in the large intestine.

Sessile colon polyps are usually benign (noncancerous). However, they can be precancerous or develop into cancer.

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 precancerous and need to be removed.
• 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 than other types, but it also carries an increased risk of becoming cancerous.
• Tubulovillous: This type of polyp has both tubular and villous growth.

What Are the Symptoms of a Sessile Polyp?

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 symptoms until they grow larger and become cancerous.

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

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, they can block the inside of the large intestine (the lumen). This can mean that stool can’t 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 bleeding polyp can cause stool to appear dark or black.
• Diarrhea: Diarrhea could result from only liquid stool passing the blocked area of the intestine. If symptoms persist for three or more days, speak to a medical professional.
• Pain: Pain is not a common symptom until polyps grow large enough to 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 hemorrhoids unless 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 pain.

What Causes Sessile Polyps?

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.

Risk Factors

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.

How Is a Sessile Polyp Diagnosed?

Two broad categories into which colon polyps are usually placed are neoplastic and non-neoplastic. In most cases, non-neoplastic polyps do not become cancerous.

Hamartomatous, hyperplastic, lymphoid, and inflammatory polyps are non-neoplastic polyps.

Neoplastic polyps may increase cancer risk, 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 with a history of an inflammatory digestive condition such as Crohn’s disease or ulcerative colitis.

Screening Options for Polyps

Screening options for finding polyps in the colon include:

• Colonoscopy, to remove polyps and provide tissue samples when a 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, a less-invasive imaging of the colon
  

How Are Sessile Polyps Treated?

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

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

• The type of polyps that were found
• The number of polyps found
• The polyps' size
• If any cancerous cells were found on a biopsy

If biopsy results show that a polyp is cancerous, it must 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 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.

What Is the Cancer Risk for Sessile Polyps?

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 the colon, finding less visually obvious sessile polyps may be more challenging.

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 polyps are growing in their colon because there are usually no symptoms.

When to See a Healthcare Provider

Since sessile polyps typically do not cause symptoms, they usually go undetected until a routine colon cancer screening.

Colon cancer screenings guidelines recommend routine colon cancer screenings for all adults ages 45 to 75. Adults aged 76 and 85 should discuss colon cancer screenings with their healthcare provider.

Screening in people younger than 45 is recommended for those with: 

• Inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis
• A family or personal history of colorectal cancer or colorectal polyps
• Some genetic syndromes, such as familial adenomatous polyposis or hereditary non-polyposis colorectal cancer

The U.S. Preventive Services Task Force recommends the following colorectal cancer screening frequency:

• Every 1 to 3 years: Stool tests, such as high-sensitivity guaiac fecal occult blood test (gFOBT), fecal immunochemical test (FIT), and stool DNA test.
• Every 5 years: Direct visual test with CT colonography or flexible sigmoidoscopy
• Every 10 years: Colonoscopy 

Summary

Sessile polyps are flat or dome-shaped abnormal growths in the colon's lining. They are typically asymptomatic and often found during a routine colon cancer screening and may be treated during a colonoscopy.  

Colon polyps are usually benign, but all colon cancers begin as polyps. Sessile serrated adenomas are more likely to be precancerous than other types of sessile polyps. 

Sessile polyps are more common in people who are Black, over 50, smoke, and those who have diabetes or obesity.

Routine colon cancer screenings should begin at age 45—and younger if you're at high risk for colon cancer. If you are over 75 and do not have a history of polyps or colon cancer, you may no longer need screening.