Tubulovillous adenoma of the colon

This article will help you read and understand your pathology report for tubulovillous adenoma of the colon.

by Ipshita Kak MD FRCPC, updated January 7, 2021

Quick facts:

• A tubulovillous adenoma is a non-cancerous tumour that develops from the cells that line the inside of the colon.
• Tubular adenomas are a common type of polyp in the colon.
• Large tubulovillous adenomas and those with high grade dysplasia are associated with an increased risk for developing colon cancer.

The anatomy of the colon

The colon is a part of the gastrointestinal tract which also includes the mouth, esophagus, stomach, small bowel, and anus. The colon is a long hollow tube that starts at the small bowel and ends at the anal canal. The colon is divided into sections which include the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum. The functions of the colon are to absorb water from the food that we eat and to move waste out of the body.

The colon is made up of six layers of tissue:

1. Mucosa – The mucosa is the tissue that lines the inside surface of the colon. The mucosa includes epithelial cells that form structures called glands. The glands are surrounded and supported by a tissue called lamina propria.
2. Muscularis mucosa – This is a thin layer of muscle that sits just below the mucosa.
3. Submucosa – The submucosa contains many thick blood vessels and lymphatic channels.
4. Muscularis propria – The muscularis propria is a thick bundle of muscle. The muscles in the muscularis propria help move digested food and waste along the colon.
5. Subserosal adipose tissue – This is a layer of fat that sits directly below the muscularis propria. The subserosal adipose tissue is near the outside surface of the colon.
6. Serosa – The serosa is a thin layer of tissue that covers the subserosal adipose tissue and the outside of the colon.

What is a tubulovillous adenoma?

Tubulovillous adenoma is a non-cancerous growth that develops from the glands in the mucosa. These adenomas can develop anywhere along the length of the colon. Tubulovillous adenomas are important because some will develop changes that can lead to a type of colon cancer called adenocarcinoma over time.

Colonoscopy

Examination of the colon in a procedure known as a colonoscopy and removal of any polyps has been shown to reduce the risk of developing colon cancer in older adults. The type, size, and number of polyps removed at your first colonoscopy will determine the period within which your doctor will ask you to come back for a follow-up endoscopy.​

Dysplasia

When examined under the microscope, tubulovillous adenomas are made up of cells that show an abnormal pattern of growth. Pathologists call this abnormal pattern of growth dysplasia. Dysplasia in the colon is important because it is considered a precancerous condition that can turn into a cancer over time.

In the colon, pathologists divide dysplasia into two categories called low grade dysplasia and high grade dysplasia. All tubulovillous adenomas show at least low grade dysplasia. Your pathologist will carefully examine your tissue sample to look for any high grade dysplasia.

The risk for developing cancer is greater with high grade dysplasia.

Margins

​In the colon, a margin is any tissue that was cut by the surgeon in order to remove the tubulovillous adenoma from your body. Many 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.

Dysplasia at the cut edge of the tissue means that the abnormal tissue may not have been completely removed from the body.

Tubulovillous adenomas are often removed and sent to pathology as multiple pieces (fragments) of tissue. In some of these cases, it will 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.