Tubulovillous adenoma of the colon and rectum

by Jason Wasserman MD PhD FRCPC
January 27, 2023

What is a tubulovillous adenoma?

A tubulovillous adenoma (TVA) is a noncancerous type of polyp that can develop anywhere in the colon and rectum. It develops from the cells that cover the inside surface of these tissues. If left untreated, all tubulovillous adenomas are associated with an increased risk of developing a type of colon cancer called adenocarcinoma over time.

Does tubulovillous adenoma mean cancer?

No, tubulovillous adenoma does not mean cancer. However, all tubulovillous adenomas are considered precancerous growths because they can turn into a type of colon cancer called adenocarcinoma over time.

What is the difference between a tubulovillous adenoma and a polyp?

In pathology, the term polyp is used to describe any growth that sticks out from the surface of a tissue. Because of the way they grow, tubulovillous adenomas are a type of polyp. However, not all polyps in the colon are tubulovillous adenomas. Other types of polyps in the colon include tubular adenomas, villous adenomas, and sessile serrated lesions.

How is the diagnosis of tubulovillous adenoma 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 in multiple pieces.

What does a tubulovillous adenoma look like under the microscope?

When examined under the microscope, the cells in parts of the tubulovillous adenoma connect together to form long, thin finger-like projections called villi. In other areas, the cells in the adenoma connect together to form tube-shaped glands. The nuclei (the part of the cell that holds the genetic material) of the cells in the adenoma are also larger and hyperchromatic (darker) compared to the cells normally found on the inside surface of the colon.

What does dysplasia mean and why is it important 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. Pathologists divide dysplasia into two levels when examining a tubulovillous adenoma: 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 adenocarcinoma. If possible, all tubulovillous adenomas with high grade dysplasia should be removed completely.

What is a margin and why is it important?

A margin is any tissue that was cut by the surgeon in order 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.

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