Tubulovillous adenoma of the large intestine

by Jason Wasserman MD PhD FRCPC
April 9, 2024

A tubulovillous adenoma is a type of polyp found in the large intestine, including the colon and rectum. It starts from glandular cells that cover the inside surface of the intestine. Tubulovillous adenomas are considered precancerous conditions because, while most are benign (non-cancerous), they have the potential to develop into colorectal cancer called adenocarcinoma over time if left untreated.

Symptoms of a tubulovillous adenoma

Tubulovillous adenomas often do not cause any symptoms, especially in the early stages, and are usually found during routine colonoscopy screenings. When symptoms do occur, they may include:

• Blood in the stool or rectal bleeding.
• Mucus in the stool.
• Changes in bowel habits, such as diarrhea or constipation.
• Abdominal pain or discomfort.

In some cases, large adenomas can lead to more significant issues like bowel obstruction or contribute to iron deficiency anemia due to chronic blood loss.

What causes a tubulovillous adenoma

The development of tubulovillous adenomas is influenced by a combination of genetic and environmental factors, though the exact cause is not fully understood. Known risk factors include:

• Aging, with a higher risk in individuals over 50.
• A family history of colorectal cancer or adenomatous polyps.
• Lifestyle factors, including diet, physical inactivity, obesity, and smoking.
• Certain genetic conditions, such as familial adenomatous polyposis (FAP) and Lynch syndrome.

How is this diagnosis made?

The diagnosis of tubulovillous adenoma can only be made after part or all of the adenoma is removed, and the tissue is examined under the microscope by a pathologist. The adenoma may be removed in one piece or multiple pieces.

Microscopic features

A tubulovillous adenoma of the large intestine exhibits characteristics of both tubular and villous adenomas. The adenoma is  composed of dysplastic epithelial cells forming tubular (glandular) and villous (finger-like) structures, hence the name. Compared to normal cells, these dysplastic cells exhibit increased nuclear size, hyperchromasia (increased staining intensity), and a higher nucleus-to-cytoplasm ratio.

Low versus high grade dysplasia in a tubulovillous adenoma

All tubulovillous adenomas show an abnormal pattern of growth called dysplasia. Dysplasia is important because it is a precancerous change that can become cancerous over time. When examining a tubulovillous adenoma, pathologists divide dysplasia into two levels: low grade dysplasia and high grade dysplasia.

Tubulovillous adenoma with low grade dysplasia

Low grade dysplasia is an early precancerous change seen in most tubulovillous adenomas. If left untreated, low grade dysplasia can change into high grade dysplasia or cancer over time. However, the overall risk is low.

Tubulovillous adenoma with high grade dysplasia

High grade dysplasia is a more advanced precancerous change seen in a small number of tubulovillous adenomas. If left untreated, tubulovillous adenomas with high grade dysplasia can turn into a type of colon cancer called invasive adenocarcinoma. If possible, all tubulovillous adenomas with high grade dysplasia should be removed completely.

​Margins

A margin is any tissue that was cut by the surgeon to remove the tubulovillous adenoma from your body. Dysplasia at the cut edge of the tissue means that the abnormal tissue may not have been completely removed from the body.

Some tubulovillous adenomas grow on a piece of tissue called a stalk and the adenoma is removed by cutting the stalk. In these cases, the margin is the part of the stalk that is cut. However, most tubulovillous adenomas are removed and sent to pathology as multiple pieces (fragments) of tissue. In these cases, it may not be possible for your pathologist to determine which piece is the real margin and the changes seen at the margin will not be described in your report.