Sessile polyps develop on the mucosa, the tissue that lines the colon and other organs. They are flat and round and mostly harmless, but some can become cancerous.

Polyps often occur in the bladder, stomach, nose, gallbladder, and cervix, but they are most commonly present in the colon.

Polyps can be peduncled or sessile. Peduncled polyps grow on stalks, whereas sessile polyps lie flat in the shape of domes.

About 20–30% of adults in the United States develop colon polyps. These are often benign, but they can sometimes become cancerous. Due to this, it is important to monitor polyps, and, in some cases, it may be best to remove them completely.

In this article, we discuss sessile polyps in more detail, including the different types, possible causes, and treatment options.

A sessile polyp is a flat mass that arises from the mucosal layer of a hollow organ within the body. These polyps grow flat on the tissue lining the organ and may blend in with it. Their lack of visibility can make them difficult to find and treat.

Sessile polyps are often precancerous, meaning that cancer can develop in them, but they can also be benign or cancerous. Doctors may find them during a colonoscopy and will often remove them to prevent the risk of cancer developing.

Polyps can also be peduncled. Rather than forming a flat dome, as with sessile polyps, peduncled polyps extend out on stalks. This structure gives peduncled polyps a mushroom-like appearance.

Common types of sessile polyp include:

  • hyperplastic
  • sessile serrated
  • tubular
  • tubulovillous

Each of these four categories has the potential to turn into colorectal cancer, but this is most likely in cases of sessile serrated polyps.

The sessile serrated form is one of three categories of serrated polyps. Of these categories, the sessile serrated polyp is the most challenging to identify, hardest to remove, and most likely to develop into cancer.

Sessile serrated polyps are common and tend to carry a low risk of becoming cancerous as long as they do not contain major cellular changes. However, they have significant cancer potential if they show signs of dysplasia.

There are various theories as to why sessile polyps may develop.

Research suggests that sessile serrated polyps result from a combination of a mutation in a gene called BRAF and a process called promoter hypermethylation, which makes cells more likely to become cancerous. Put simply, the mutated gene causes cells to divide, which the body is unable to prevent.

Certain risk factors make a person more likely to develop colon polyps. These risk factors vary slightly among types of sessile polyps. For example, people are more likely to develop sessile serrated polyps, if they:

Many risk factors and causes overlap between the categories of polyps but have different strengths of influence. Genetic factors can also play a role.

Most of the time, sessile polyps do not cause any symptoms. In many cases, a doctor may only discover polyps during a medical exam or colonoscopy.

However, in some cases, polyps in the colon may cause symptoms, such as:

  • stomach pain
  • alterations to bowel movements
  • blood in the feces

A doctor can perform a colonoscopy to identify polyps in the colon. During this procedure, the doctor will observe the large intestine and part of the small intestine through a colonoscope.

The colonoscope, which is effectively a camera on a tube that provides images of the walls of the colon, allows the doctor to see whether there are polyps present. The flatter the sessile polyps are, the harder they are to identify.

The doctor may also carry out a biopsy, which involves taking tissue from the polyps to determine their type and whether they are likely to develop into cancer.

Sessile polyps may not always require treatment. If a doctor identifies them to be harmless, they may decide to leave the polyps but monitor them on a regular basis.

People with a history of polyps have a higher chance of developing more in the future, increasing their risk of developing cancerous polyps. Therefore, a doctor may schedule more frequent checkups with these individuals.

If polyps are cancerous or have the potential to become so, the doctor is likely to recommend removing them. If the polyps are in an accessible position, the doctor may be able to extract them at the time of the colonoscopy using a procedure called a polypectomy.

During a colon polypectomy, the doctor can use different surgical techniques to remove polyps. Some options include cold forceps polypectomy, hot forceps polypectomy, and snare polypectomy.

If the polyps are already cancerous by the time of diagnosis and the cancer has spread elsewhere, the person may need to undergo radiation therapy or chemotherapy.

Doctors classify polyps as either neoplastic or non-neoplastic.

Non-neoplastic categories generally cause less concern as they do not have the potential to become cancerous. Conversely, neoplastic variations are important to identify, as they may lead to colorectal cancer.

Sessile serrated polyps are an example of neoplastic polyps. They are one of the most concerning types of polyp because a person can go for years without realizing that they are present. During this time, the unmonitored polyps may develop into cancer.

As polyps often appear without symptoms, it is a good idea to go for regular checkups.

A doctor can check to see whether polyps are present and take a biopsy to determine how likely they are to develop into cancer.

A sessile polyp is a flat or dome shaped mass that extends out from the mucosal layer in hollow organs. These polyps can be neoplastic or non-neoplastic. As neoplastic polyps have the potential to become cancerous, it is important to have a doctor diagnose and remove them, if necessary.

Polyps can develop in different parts of the body, but they most commonly occur in the colon. They are particularly common for individuals over the age of 50 years. As they often do not cause symptoms, it is important to go for regular checkups to maximize the chance of early diagnosis and a good outcome.