Tubulovillous adenoma of the colon and rectum

by Jason Wasserman MD PhD FRCPC
July 18, 2025

A tubulovillous adenoma is a type of polyp that develops on the inner lining of the large intestine, which includes the colon and rectum. It is composed of abnormal glandular cells that form both tube-shaped structures (known as tubular architecture) and finger-like projections (referred to as villous architecture). Tubulovillous adenomas are considered precancerous because, over time, the abnormal cells can turn into a type of colorectal cancer called adenocarcinoma. Most tubulovillous adenomas are discovered during routine screening colonoscopies and are removed to prevent cancer from developing.

Is a tubulovillous adenoma a type of cancer?

No, a tubulovillous adenoma is not cancer. It is a benign (non-cancerous) growth. However, because the cells inside the adenoma are abnormal (a condition called dysplasia), and because the villous component is associated with a higher risk of progression, tubulovillous adenomas are considered precancerous and are typically removed.

What are the symptoms of a tubulovillous adenoma?

Most people with a tubulovillous adenoma do not have any symptoms. These polyps are often found during routine colonoscopy screening. However, if symptoms do occur, they may include:

• Rectal bleeding or blood in the stool.

• Changes in bowel habits such as constipation or diarrhea.

• Abdominal discomfort or pain.

What causes a tubulovillous adenoma?

Tubulovillous adenomas develop when genetic changes called mutations in the cells lining the colon cause them to grow abnormally. Most of these changes are acquired over time rather than inherited.

Risk factors include:

• Age over 50.

• A family history of colorectal cancer or polyps.

• Certain inherited conditions such as familial adenomatous polyposis (FAP).

• Lifestyle factors such as smoking, obesity, a high-fat diet, and low physical activity.

How is this diagnosis made?

A diagnosis of tubulovillous adenoma is made after the polyp is removed during a colonoscopy and examined under a microscope by a pathologist. Sometimes the entire polyp is removed in one piece, but in other cases, it may be removed in smaller fragments. The tissue is then studied to determine the type of adenoma and whether it contains abnormal or precancerous cells.

What does a tubulovillous adenoma look like under the microscope?

Under the microscope, a tubulovillous adenoma is made up of abnormal glandular cells that grow in both tubular (tube-like) and villous (finger-like) patterns. To be classified as tubulovillous, between 25% and 75% of the adenoma must show villous architecture. The abnormal cells often show changes in shape, size, and organization. These changes are described as dysplasia, and all tubulovillous adenomas contain some degree of dysplasia.

Low grade versus high grade dysplasia in a tubular adenoma

All tubulovillous adenomas show dysplasia, which is a term pathologists use to describe cells that are growing abnormally but are not yet cancer. Dysplasia is important because it helps determine how likely the adenoma is to progress into cancer if left untreated. Pathologists divide dysplasia into two levels: low grade and high grade.

Tubulovillous adenoma with low grade dysplasia

In a tubulovillous adenoma with low grade dysplasia, the cells show mild to moderate abnormalities. The nuclei (the control centers of the cells) may be enlarged, darker than normal, and arranged in a slightly disorganized way. However, the overall structure of the glands remains relatively intact. Low grade dysplasia is considered early in the process of abnormal cell development. Most tubulovillous adenomas with low grade dysplasia do not become cancer, especially if they are completely removed.

Tubulovillous adenoma with high grade dysplasia

In a tubulovillous adenoma with high grade dysplasia, the cells show more advanced and severe abnormalities. The nuclei are very large, misshapen, and disorganized, and the normal architecture of the glands is often lost. These changes mean that the cells are closer to becoming cancer. A tubulovillous adenoma with high grade dysplasia is still not cancer, but the risk of progression is higher, and complete removal is strongly recommended.

What does it mean if the margin is mentioned in the pathology report?

The margin is the edge of tissue where the polyp was removed during colonoscopy. If the margin is free of abnormal cells, it suggests that the entire polyp was removed. However, if the margin contains dysplastic cells, it may mean that part of the polyp was left behind. In many cases, especially when the polyp is removed in multiple fragments, it may not be possible to assess the margin. Your pathologist will describe what was seen and your doctor will let you know if any follow-up is needed.

What is the risk of developing cancer?

Tubulovillous adenomas have a greater risk of turning into cancer compared to purely tubular adenomas, especially if they are larger in size or show high grade dysplasia. This is why doctors recommend removing all tubulovillous adenomas and monitoring with follow-up colonoscopies to look for new polyps.

Can a tubulovillous adenoma come back after being removed?

If the entire polyp is removed, it usually does not grow back in the same location. However, new adenomas may develop elsewhere in the colon or rectum over time. This is why your doctor may recommend repeat colonoscopies based on the size, type, and number of adenomas that were found.

Questions to ask your doctor

• Was the entire adenoma removed during the colonoscopy?

• Did the pathology report describe low grade or high grade dysplasia?

• How much villous architecture was present in the adenoma?

• Were the margins free of dysplasia?

• When should I return for my next colonoscopy?