Tubulovillous Adenoma of the Colon and Rectum: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
August 16, 2026

A tubulovillous adenoma is a type of precancerous polyp that develops on the inner lining of the large intestine, which includes the colon and the rectum. It is made up of abnormal glandular cells that grow in two different shapes: tube-shaped glands, described as tubular, and long finger-shaped projections, described as villous. Tubulovillous adenomas are not cancer, but they can slowly change into a type of cancer called adenocarcinoma if they are left in place, so they are removed when they are found.

Compared with a tubular adenoma, which is the most common type of colon polyp, a tubulovillous adenoma carries a higher risk of progressing to cancer. This article explains the findings you may see in a pathology report after a tubulovillous adenoma has been removed, what each one means, and why the villous part of the diagnosis changes your follow-up plan.

Is a tubulovillous adenoma cancer?

No. A tubulovillous 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 a long period of time if it were not removed. Most tubulovillous adenomas never reach that point, and taking the polyp out during colonoscopy interrupts the process.

What causes a tubulovillous adenoma?

Tubulovillous adenomas develop when cells in the lining of the colon or rectum acquire mutations, which are errors in their DNA that allow the cells to grow in an abnormal, disorganized way. The earliest change usually affects a tumor suppressor gene called APC, which normally acts as a brake on cell division. When that brake is lost, the cells lining the bowel pile up and form a polyp. As the polyp grows, further errors accumulate, which is part of why larger polyps carry more risk than smaller ones.

Factors that increase the chance of developing a tubulovillous adenoma include:

Increasing age. Adenomas become steadily more common after age 45, which is why screening colonoscopy is offered from that age for people at average risk.
A personal or family history of colon polyps or colorectal cancer.
Inherited conditions that cause many polyps to form, such as familial adenomatous polyposis (FAP) and Lynch syndrome. These conditions account for only a small minority of adenomas.
Long-standing inflammatory bowel disease, including ulcerative colitis and Crohn’s disease.
Lifestyle factors, including smoking, heavy alcohol use, excess body weight, physical inactivity, and a diet high in red and processed meat and low in fiber.

Finding a single tubulovillous adenoma is common and does not by itself suggest an inherited condition.

What are the symptoms of a tubulovillous adenoma?

Most tubulovillous adenomas cause no symptoms and are found by chance during a screening colonoscopy. Because these polyps tend to be larger than tubular adenomas by the time they are found, symptoms are somewhat more likely and may include blood in the stool, rectal bleeding, or a change in bowel habits such as constipation or diarrhea. Bleeding may also be invisible to the eye, and stool-based screening tests are designed to detect this kind of hidden bleeding.

Large polyps with extensive villous growth in the rectum can sometimes produce noticeable mucus in the stool. Rarely, a very large villous polyp releases enough fluid and salts to cause watery diarrhea and dehydration.

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?

Doctors diagnose a tubulovillous adenoma only after removing the polyp and examining it under a microscope. Doctors usually remove the polyp during a colonoscopy using a procedure called polypectomy, in which a wire loop or a pair of biopsy forceps is passed through the scope to remove the growth. Because tubulovillous adenomas are often larger and flatter than tubular adenomas, they are more likely to require endoscopic mucosal resection, a technique that lifts and removes a wider area of the lining, or to be removed in several pieces rather than one.

Tubulovillous adenoma

The tissue is then sent to a pathology laboratory, where a pathologist examines it under a microscope. In a tubulovillous adenoma, the glands are abnormal in both shape and cell appearance: some grow as crowded tubes and others as tall finger-shaped fronds, and the cells lining them have darker, more crowded nuclei than the surrounding normal colonic mucosa. These abnormal changes are called dysplasia, and by definition every adenoma shows dysplasia. The pathologist also confirms that the abnormal cells have not grown into the tissue beneath the lining, which would change the diagnosis to cancer.

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

Growth pattern

The words tubular, tubulovillous, and villous describe the shape of the glands the pathologist sees in the polyp, and they divide colon and rectal adenomas into three types. Most adenomas contain some of both shapes, so the diagnosis depends on the proportion of villous growth:

Tubular adenoma. Less than 25% villous growth. This is the most common type and carries the lowest risk of progressing to cancer.
Tubulovillous adenoma. Between 25% and 75% villous growth.
Villous adenoma. More than 75% villous growth. This is the least common type and carries the highest risk.

Estimating the proportion of villous growth involves judgment rather than measurement, and two pathologists reviewing the same polyp will not always place it in the same category, particularly near the 25% and 75% boundaries. For your follow-up, what matters most is whether a villous component was identified, since any villous component places the polyp in a higher-risk group. The exact percentage does not change that.

Dysplasia

Every tubulovillous adenoma shows dysplasia, a word pathologists use for cells that look abnormal under the microscope but are not yet cancer. The report will describe the dysplasia as one of two grades, and this grade is one of the findings that most influences your follow-up plan.

Low grade dysplasia. The cells look mildly abnormal. Their nuclei are enlarged, darker, and more crowded than normal, but the glands keep their usual orderly arrangement. This is the most common finding in a tubulovillous adenoma.
High grade dysplasia. The cells look markedly abnormal, with large, irregular nuclei and prominent nucleoli, 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, so complete removal and earlier follow-up are important.

High grade dysplasia is found more often in tubulovillous adenomas than in tubular adenomas, because both the villous growth pattern and high grade dysplasia tend to appear as a polyp becomes larger and older. As with growth pattern, grading involves judgment, and a second pathologist may review the slides in a borderline case.

Size and number of polyps

Two other findings recorded after a tubulovillous adenoma is removed are the polyp’s size and the total number of polyps found. Both influence how soon the next colonoscopy is recommended.

Size is usually reported in millimeters, and the threshold that matters most is 10 mm, roughly the width of a fingernail. Tubulovillous adenomas are more often 10 mm or larger than tubular adenomas are. You may notice that the size in the pathology report differs slightly from the size your endoscopist described, because the polyp is measured both during the procedure and again in the laboratory, and tissue changes shape once it is removed and preserved.

The total number of adenomas removed also matters. Finding three or more, and particularly finding ten or more, places you in a higher risk group and may prompt your doctor to consider testing for an inherited polyp condition.

Margins

The margin is the cut edge of the tissue removed during the polypectomy. The pathologist examines it to determine whether the whole tubulovillous 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 may 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.

Margin status carries more weight for a tubulovillous adenoma than for a small tubular adenoma. These polyps are larger and more often removed in fragments, and residual tissue left behind is the most common reason a polyp appears to recur. When the polyp was removed piecemeal or the margin was positive, your doctor will usually arrange a separate look at that specific area rather than waiting for the routine surveillance interval.

Advanced adenoma

Your doctor may describe a tubulovillous adenoma as an advanced adenoma. This is not a separate diagnosis but a risk category that gathers together several findings. An adenoma is called advanced if it has any one of the following features:

A villous component, meaning the polyp is a tubulovillous or villous adenoma.
A size of 10 mm or larger.
High grade dysplasia.

Because a villous component is one of the three criteria, every tubulovillous adenoma is an advanced adenoma, regardless of its size or the grade of dysplasia. This is the most important difference between this diagnosis and a small tubular adenoma, and it is why your next colonoscopy will be recommended sooner than for most polyps.

What is the risk that a tubulovillous adenoma will become cancer?

Most tubulovillous adenomas never become cancer. The change from adenoma to colorectal adenocarcinoma is slow, typically taking a decade or more, and only a minority of adenomas complete it. That said, the risk is higher than for a tubular adenoma, and it rises further with increasing size and with high grade dysplasia.

This slow timeline is what makes colonoscopy effective. Removing adenomas before they progress substantially lowers the risk of developing colorectal cancer, which is why doctors remove polyps when they find them rather than watch them.

Two related terms sometimes appear on reports for larger adenomas 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 polyp is no longer a simple tubulovillous adenoma, and your doctor will discuss what it means for you.

What happens after this diagnosis?

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

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

A tubulovillous adenoma, completely removed. The next colonoscopy is generally considered at 3 years, because any adenoma with a villous component counts as an advanced adenoma.
A tubulovillous adenoma with high grade dysplasia, or 10 mm or larger. Also generally 3 years, since these features place the polyp in the same category rather than a separate one.
More than ten adenomas in total. Generally within 1 year, along with consideration of testing for an inherited polyp condition.
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.

These intervals are a starting point rather than a rule, and the quality of the examination itself matters. 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 factors your doctor weighs when setting the plan, and it also describes what happens after your pathology report.

Having one adenoma removed does not mean more will form, but it does place you at somewhat higher risk than someone who has never had one, which is why ongoing surveillance is recommended rather than a return to routine screening.

Questions to ask your doctor

Where in the colon or rectum was the polyp found?
Did my report describe low grade or high grade dysplasia?
How large was the polyp, and how many polyps were removed in total?
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?
Since a tubulovillous adenoma counts as an advanced adenoma, when should my next colonoscopy be?
Was the bowel preparation good enough for a complete examination?
Does this finding change my overall risk of colorectal cancer?
Should my children, siblings, or parents start screening earlier than usual?
Is there anything in my history that suggests I should be tested for an inherited polyp condition?
Are there changes to my diet, weight, alcohol use, or smoking that would lower my risk of new polyps?