Traditional Serrated Adenoma: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCP
August 17, 2026

A traditional serrated adenoma, often shortened to TSA, is a precancerous polyp that develops on the inner lining of the large intestine, including the colon and rectum. It is not cancer, but it can change into a cancer called adenocarcinoma if it is left in place, so it is removed when it is found.

Traditional serrated adenomas are the least common type of colon polyp pathologists regularly diagnose, accounting for only about 1% of all polyps removed at colonoscopy. They belong to the serrated family of polyps, alongside sessile serrated lesions and hyperplastic polyps, and they occur most often in the rectum and the lower part of the colon. This article explains what you may see in a pathology report after a traditional serrated adenoma has been removed, what each finding means, and why this uncommon diagnosis requires closer follow-up than most polyps.

Is a traditional serrated adenoma cancer?

No. A traditional serrated adenoma is a precancerous polyp, not cancer. The abnormal cells inside it are confined to the surface lining of the bowel and have not grown down into the deeper tissue underneath. That downward growth, called invasion, is what separates a precancerous polyp from cancer.

Precancerous means the polyp could turn into cancer over time if it were not removed. Traditional serrated adenomas are treated as a higher-risk polyp type, so removal and a shorter interval before the next colonoscopy are standard, but the polyp itself is not a cancer diagnosis.

What causes a traditional serrated adenoma?

Traditional serrated adenomas develop when cells in the lining of the colon or rectum acquire mutations, which are errors in the DNA that allow the cells to grow abnormally. Like other serrated polyps, they follow what pathologists call the serrated pathway to cancer, which differs from the route taken by conventional adenomas such as the tubular adenoma.

Two different gene changes can start a traditional serrated adenoma, and which one is involved tends to track with where the polyp is found:

KRAS mutation. More common in polyps in the rectum and the lower colon, which is where most traditional serrated adenomas occur.
BRAF mutation. More common in polyps higher up in the colon. These often appear to grow out of a pre-existing serrated polyp, such as a sessile serrated lesion or a hyperplastic polyp, and a report may describe both components in the same specimen.

Many traditional serrated adenomas also carry a change affecting a group of genes called RSPO, which increases signaling that tells the cells lining the bowel to keep dividing. These molecular details are not usually tested for or reported after a polyp is removed, and they do not change what happens next for you. They are the reason pathologists group this polyp separately from the others.

Age, smoking, heavy alcohol use, excess body weight, physical inactivity, and a family history of colorectal cancer or polyps all increase the chance of developing serrated polyps generally.

What are the symptoms of a traditional serrated adenoma?

Most traditional serrated adenomas cause no symptoms and are found by chance during a screening colonoscopy. Because these polyps are often raised and sit low in the colon or rectum, blood in the stool or rectal bleeding is somewhat more likely than with a flat serrated polyp higher up. A change in bowel habits or mucus in the stool occurs occasionally.

None of these symptoms can tell you whether a polyp is present, since many other conditions cause them. Only examination of the bowel and microscopic examination of the tissue removed can do that.

How is the diagnosis made?

A pathologist makes the diagnosis of a traditional serrated adenoma only after the polyp is removed and examined under a microscope. During a colonoscopy, a procedure called a polypectomy removes the polyp using a wire loop passed through the scope. Larger polyps may require endoscopic mucosal resection, a technique that lifts and removes a wider area of the lining.

Under the microscope, a traditional serrated adenoma has a distinctive appearance that sets it apart from every other colon polyp. The surface forms tall projections, and the glands within them have a saw-tooth outline with narrow, slit-shaped notches. The cells lining these glands are tall and column-shaped with brightly pink cytoplasm, the material that fills a cell around its nucleus. Small buds of gland tissue, called ectopic crypts, often sprout from the sides of the projections without reaching down to the base of the lining as normal glands do. These features allow the pathologist to distinguish this polyp from a sessile serrated lesion, a hyperplastic polyp, and a conventional adenoma.

Because a traditional serrated adenoma is not cancer, no imaging scans are needed after the diagnosis.

Dysplasia

Dysplasia is the word pathologists use for cells that look abnormal under the microscope but are not yet cancer. By definition, every traditional serrated adenoma shows dysplasia, which is why the word adenoma appears in its name. This separates it from a sessile serrated lesion, where dysplasia is usually absent and its presence is an important added finding.

Your report will describe the dysplasia in a traditional serrated adenoma as one of two grades:

Low grade dysplasia. The cells look mildly abnormal, and the glands keep their usual orderly arrangement. This is the usual finding.
High grade dysplasia. The cells look markedly abnormal, with large, irregular nuclei, and the glands lose their orderly arrangement and crowd together. High grade dysplasia is still not cancer, but it sits closer to cancer along the same pathway.

Because a traditional serrated adenoma is already treated as a higher risk polyp, finding low grade rather than high grade dysplasia does not shorten the interval before your next colonoscopy the way it would for a small tubular adenoma. High grade dysplasia may prompt your doctor to look again sooner still.

Size and number of polyps

Two other findings recorded after a traditional serrated adenoma is removed are the polyp’s size and the total number of polyps found.

Size is usually reported in millimeters, and the threshold that matters most across colon polyps is 10 mm, roughly the width of a fingernail. For a traditional serrated adenoma, size matters less for follow-up than for how the removal site is checked afterward, since this diagnosis already places you in a higher-risk group at any size. A polyp of 20 mm or larger that was removed in pieces is usually rechecked separately.

The number of polyps also matters. Traditional serrated adenomas are sometimes found alongside other serrated polyps, and finding many serrated polyps raises the possibility of serrated polyposis syndrome, a condition defined by either at least five serrated polyps above the rectum with two or more of them 10 mm or larger, or more than twenty serrated polyps of any size spread throughout the colon. It carries an increased risk of colorectal cancer and leads to a much shorter surveillance interval.

Margins

The margin is the cut edge of the tissue removed during the polypectomy. The pathologist examines it to determine whether the entire traditional serrated adenoma was removed. Your report will describe the margin in one of three ways:

Negative (clear) margin. No abnormal cells are seen at the cut edge. The polyp appears to have been removed completely.
Positive margin. Abnormal cells reach the cut edge, so some polyp tissue may remain in the bowel. Your doctor will usually arrange a repeat examination of that area.
Cannot be assessed. Larger polyps are often removed in several pieces, and the edges of the tissue are frequently sealed with heat during removal, leaving a cautery artifact. Either situation can make the margin impossible to evaluate reliably. This is common and expected, not a sign that something went wrong.

Complete removal matters for this diagnosis because tissue left behind is the usual reason a polyp reappears on a later colonoscopy.

How is a traditional serrated adenoma different from other serrated polyps?

Three types of polyp make up the serrated family, and a traditional serrated adenoma differs from the other two in ways that affect what your report says and what happens next.

Traditional serrated adenoma. Uncommon. Usually raised, usually in the rectum or lower colon. Always shows dysplasia. Treated as a higher-risk polyp.
Sessile serrated lesion. Much more common. Flat and usually in the upper colon. Usually shows no dysplasia, and when dysplasia is present, it is a significant added finding.
Hyperplastic polyp. The most common of the three. Usually small and in the rectum or lower colon. Not precancerous in most cases.

Despite the word adenoma in its name, a traditional serrated adenoma is not the same as a tubular, tubulovillous, or villous adenoma. Those are conventional adenomas, which reach cancer by a different genetic route. The shared word refers only to the presence of dysplasia.

What is the risk that a traditional serrated adenoma will become cancer?

A traditional serrated adenoma carries a higher risk of progressing to colorectal adenocarcinoma than most polyps, which is why it is grouped with advanced adenomas for follow-up. The risk rises further when the polyp is 10 mm or larger, when it shows high grade dysplasia, and when it sits in the upper part of the colon.

Most traditional serrated adenomas are removed long before cancer develops. Removing the polyp reduces risk at that site, but it does not eliminate the risk of new polyps forming elsewhere in the colon, which is why surveillance continues.

Two related terms sometimes appear on reports for larger polyps and can be confusing. Intramucosal carcinoma means abnormal cells have moved into the lamina propria, a thin supporting layer just below the surface lining, but no further. In the colon, this does not behave like invasive cancer and is generally cured by removing the polyp. A malignant polyp is different: it means cancer has grown through into the deeper layer of the bowel wall and can potentially spread. If either term appears on your report, the diagnosis is no longer a simple traditional serrated adenoma, and your doctor will discuss what it means for you.

What happens after this diagnosis?

For a traditional serrated adenoma, removing the polyp during the colonoscopy is the whole treatment. No surgery, chemotherapy, or radiation is involved. Next, your doctor sets a follow-up interval based on your report findings, your age, your overall health, and your family history.

Current guidelines from the US Multi-Society Task Force on Colorectal Cancer group findings roughly as follows:

A traditional serrated adenoma, completely removed. The next colonoscopy is generally considered at 3 years, regardless of the size of the polyp and whichever grade of dysplasia was found. This diagnosis is placed in the same category as an advanced adenoma.
A polyp 20 mm or larger removed in pieces. A repeat examination of that specific area is usually arranged within 6 months, separately from the routine schedule above, to confirm the site is clear.
Other polyps found at the same colonoscopy. Your doctor considers everything found together, and the finding that carries the shortest interval sets the plan.
Findings that meet the criteria for serrated polyposis syndrome. Surveillance is usually every 1 to 2 years, and family members are often offered screening as well.

These intervals are a starting point, not a rule. If the bowel preparation was poor or the colonoscopy could not be completed, your doctor may recommend repeating it sooner regardless of what the polyp showed. Your pathology report is one of several things your doctor weighs when setting the plan, and what happens after your pathology report describes the wider process.

Questions to ask your doctor

Where in the colon or rectum was the polyp found?
How large was it, and how many polyps were removed in total?
Did my report describe low grade or high grade dysplasia?
Was the polyp removed in one piece or in fragments?
What did the margin show, and does it mean any tissue was left behind?
Do I need a separate follow-up look at the site where the polyp was removed, and when?
Were any other polyps found, and does any of them call for a shorter interval?
Do my findings meet the criteria for serrated polyposis syndrome?
Was the bowel preparation good enough for a complete examination?
When should I have my next colonoscopy?
Does this finding change my overall risk of colorectal cancer?
Should my close family members be screened earlier or more often?
Would quitting smoking or other changes lower my risk of developing more polyps?