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