The colon, a significant part of the digestive system, plays a role in processing waste and absorbing water. Medical screenings sometimes reveal growths, or polyps, within the colon. This article aims to clarify what a diminutive tubular adenoma is and its implications.
Understanding Colon Polyps
A colon polyp is a growth that develops on the inner lining of the colon or rectum. These growths are common, especially in individuals over 50 years old, and grow slowly. While many polyps are harmless, some can change over time and develop into colorectal cancer.
Polyps are categorized into two types: non-neoplastic and neoplastic. Non-neoplastic polyps, such as hyperplastic or inflammatory polyps, do not become cancerous. Neoplastic polyps, known as adenomas, are concerning due to their potential to become malignant.
Defining Diminutive Tubular Adenomas
An “adenoma” refers to a type of neoplastic polyp that originates from the glandular tissue lining the colon. Adenomas are the most common type of colon polyp, accounting for about 60% to 70% of all colonic polyps.
The term “tubular” describes the growth pattern of the cells within the adenoma, which form tube-like structures when viewed under a microscope. This contrasts with villous adenomas, which have finger-like or leaf-like projections, or tubulovillous adenomas, which combine both patterns. Tubular adenomas are the most prevalent type of adenoma, making up 70% to 85% of all colorectal adenomas.
“Diminutive” refers to the size of the polyp, meaning it is 5 millimeters (mm) or less in diameter. Size is a factor in assessing the risk associated with a polyp. Polyps are classified as diminutive if 5 mm or less, small if 6 to 9 mm, or large if 1 centimeter (cm) or more.
Potential for Malignant Transformation
Diminutive tubular adenomas have a very low risk of progressing to cancer. Less than 10% of tubular adenomas develop into cancer. This risk is low compared to larger adenomas or those with villous features or high-grade dysplasia.
Despite the low risk, diminutive tubular adenomas are considered precancerous lesions and are removed to prevent future malignant change. While the risk for a single diminutive polyp to develop high-grade dysplasia is low, the presence of multiple small and diminutive polyps may indicate a higher risk. The presence of any adenoma suggests an individual may be at a slightly increased risk for developing other polyps in the future.
Screening and Follow-Up
Colonoscopy is the main method for detection and removal of colon polyps, including diminutive tubular adenomas. During this procedure, a flexible tube with a camera is inserted into the colon to visualize the lining and identify growths. If polyps are found, they are removed during the same procedure, a process called polypectomy.
After removal, the polyps are sent for pathological analysis to confirm their type and check for high-risk features. Post-polypectomy surveillance is important for ongoing management. For individuals with one or two small (less than 1 cm) tubular adenomas with low-grade dysplasia, the recommended interval for the next colonoscopy is 5 to 10 years. However, if there are three or more adenomas, an adenoma 1 cm or larger, or any adenoma with villous features or high-grade dysplasia, a follow-up colonoscopy is recommended within 3 years. Adhering to these surveillance guidelines helps prevent colorectal cancer.