What Is Traditional Serrated Adenoma

Overview

Traditional serrated adenomas (TSAs) are a subtype of colon polyps. They are relatively rare compared to other colon polyp types. Around 1% of colon polyps are traditional serrated adenomas.¹ There is a small chance of them turning cancerous if they are not removed early.

What are colon polyps?

Colon polyps are tissue outgrowths of the colon wall. They occur when the cells in the colon wall multiply excessively. There are associated genetic mutations that drive the cells to multiply in this way.

Colon polyps come in different sizes ranging from a few millimetres to a few centimetres. Larger polyps are more likely to be cancerous. They can be found throughout the colon and rectum.

There are many different types of colon polyps. The type of colon polyp is generally determined by a doctor (pathologist) looking at the polyp under a microscope. They need to diagnose the type of polyp correctly as some polyps have a higher risk of turning into cancer and so should be removed. There are two main types of pre-malignant colon polyps: the adenomas polyps, which account for the majority, and a smaller group called the serrated polyps.²

What are serrated polyps?

Serrated polyps are named for their sawtooth appearance under the microscope. Roughly 20%-40% of adults of screening age will have at least 1 serrated polyp in their colon (most will be harmless).¹ There are 3 different subtypes of serrated adenomas:

• Hyperplastic polyps (HPs) (75 %)
• Sessile serrated lesions (SSLs) (25 %)
• Traditional serrated adenoma (TSAs) (<1 %)³

Hyperplastic polyps are the most common subtype of serrated polyps. These rarely develop into cancer. However, there is a greater chance of the sessile serrated lesions and traditional serrated adenomas progressing to colon cancer. However, it is still quite small. This article will focus on the rarest type of serrated polyps, the traditional serrated adenomas.

What are traditional serrated adenomas?

TSAs are generally found in the lower (distal) colon.³ They are generally larger than hyperplastic polyps and are mostly ≥ 5mm.³ Traditional serrated polyps are often derived from hyperplastic or sessile serrated polyps or found alongside them.

One major distinguishing feature of traditional serrated polyps is a ‘slit-shaped’ serration.⁴ Traditional serrated adenomas often have a distinctive internal shape and contain different cell types compared to other polyps.¹

Symptoms and Diagnosis

Symptoms

Most colon polyps do not present with symptoms, but people with larger or bleeding polyps may have symptoms. The most common symptoms are:

• Blood or slime in your faeces
• A change in the frequency of your bowel habits (diarrhoea or constipation)
• Unexplained weight loss
• Abdominal pain

Please contact your local GP or a healthcare professional if you are concerned about your symptoms.

Diagnosis

Colonoscopy

Traditional serrated adenomas are usually detected during a colonoscopy. A colonoscopy is a procedure that involves a doctor inserting a tube with a camera (colonoscope) through the patient’s anus and rectum in order to take a closer look at the colon wall. The patient is usually asked not to eat or drink for some time before a colonoscopy. This makes it easier for the doctor to visualise the colon and detect any polyps. A colonoscopy shouldn’t be painful, but it may feel uncomfortable.

Colon polyps are often detected when a doctor is looking for the cause of experienced symptoms. They could also be looking for colon cancer or inflammatory bowel disease. They are also detected during bowel cancer screening when the test detects a small amount of blood in your faeces. Most polyps are diagnosed in people over the age of 50. It is sometimes difficult to detect polyps, particularly smaller, flatter polyps, during a colonoscopy.

Traditional serrated adenomas are found in an estimated 0.1% - 0.7 % of patients undergoing colonoscopy.³ Removal of colon polyps is one of the main ways doctors prevent colon cancer from developing.

Biopsy

During a colonoscopy, the doctor may decide to remove a small portion of a polyp (biopsy) and send a sample to another doctor known as a pathologist, who will take a closer look at them under a microscope. The pathologist will look at what type of polyp it is based on the structure and the type of cells in it. They will also look for specific precancerous signs in the polyp, known as dysplasia.

It usually takes a while for the results of a biopsy to return, but once they are ready, the doctor will discuss the results and the next steps with the patient. They can discuss treatment options if required and/or recommend follow-up appointments. 

Treatment for colon polyps (polypectomy)

A decision about what to do with a colon polyp is made by a doctor. The choice of treatment is based on many different factors, but some of the most important are:

• The size of the polyp
• The age of the patient
• The type of polyp
• Whether there are cancerous or pre-cancerous cells present

The treatment for colon polyps involves their physical removal. This procedure is known as a polypectomy and is often performed during a colonoscopy. A colonoscopy (camera) is used to locate the polyp on the colon wall. Once located, the polyp is removed with a loop of wire (snare) and a hot probe to burn away the tissue.

Some smaller, flatter polyps can be difficult to remove fully and therefore, follow-up may be necessary to ensure there’s no recurrence. Follow-up duration and interval depend on the size of the polyp and whether there are more present.

It is important to attend follow-up appointments to reduce your risk of polyps reoccurring and turning into colon cancer.³

Cancer risk with serrated adenoma

The main reason why polyps need to be detected and removed is because they can turn into cancer. Most polyps don’t progress to colon cancer, but a small number do. Serrated polyps can turn into cancer via a process of mutations, and the polyp grows, and the cells turn cancerous. There is a separate mutation pathway from serrated polyps as compared to adenomas. Around 25% of colon cancers arise from serrated lesions.¹ The likelihood of a traditional serrated adenoma turning cancerous depends on the polyp size and patient characteristics (such as age and family history of cancer).

Causes and risk factors

Genetic factors

People who have a family history of colon polyps or colon cancer are more likely to develop colon polyps themselves. People who have had previous colon polyps or colon cancer are more likely to get colon polyps in the future. 

Inflammatory bowel diseases (ulcerative colitis and Crohn’s disease) are associated with developing colon polyps and colon cancer.

Serrated polyposis syndrome (SPS) is a rare condition diagnosed when there are at least 5 serrated lesions, with some of them being large.³ Patients with SPS are at higher risk of developing colon cancer and, therefore, undergo regular colonoscopy screening.

People who have had a serrated polyp in the past are more likely to have them in the future and are more likely to develop colon cancer. However, most people who have colon polyps do not develop colon cancer.⁵

Lifestyle and diet

Certain factors can increase your risk of getting traditional serrated adenomas, and these include the following:

• Being over 50 years old
• High blood pressure
• Currently smoking⁶

There is not as much research on TSA because it is relatively rare, but risk factors for serrated polyps in general include:

• Heavy alcohol drinking
• High BMI
• High fat and red meat intake²

To reduce your risk of getting colon polyps and colon cancer, it is recommended that you:

• Maintain blood pressure within the normal range
• Stop smoking if possible
• Cut down on drinking alcohol
• Lose weight
• Eat a healthy, balanced diet with plenty of fibre
• Exercise regularly

Please consult the NHS website or speak to your local doctor for more information about lifestyle changes you could make or help in implementing them.

Summary

Traditional serrated adenomas are a rare type of colon polyp. Colon polyps are outgrowths of the colon wall. Most people with colon polyps will not have symptoms, but the most common symptoms are blood or slime in your faeces, a change in the frequency of your bowel habits (diarrhoea or constipation), unexplained weight loss or abdominal pain.

They are usually detected during a colonoscopy. The doctor may decide to remove the polyp, look at it under a microscope and determine whether the polyp is cancerous. Most polyps are not cancerous, but the removal of polyps is an important step in reducing your risk of colon cancer. It will be decided whether follow-up appointments are needed to check that all the polyps have been removed and that there aren’t any new polyps or cancerous growths.

People with a family history of polyps or colon cancer are more likely to develop polyps. Polyps are more likely to be found in older people. Smoking, drinking alcohol and being overweight are some of the risk factors associated with colon polyps. It is recommended to stop smoking, cut down on drinking and try to lose weight. Please consult your local doctor for more advice or support.