Tubular adenomas are a type of polyp, or small growth, that can form on the lining of the colon or rectum. These growths originate from the glandular tissue that lines the colon. While they are considered benign, meaning non-cancerous, they are also recognized as precancerous lesions due to their potential to develop into colorectal cancer over time.
What Are Tubular Adenomas?
Tubular adenomas are the most common type of adenomatous polyp found during colonoscopies, accounting for about 80% of all adenomas detected. They are characterized by their tubular microscopic structure, where glandular tissue is arranged in tube-like formations. These adenomas are often asymptomatic, meaning they do not cause noticeable symptoms, and are frequently discovered during routine screening procedures.
The Likelihood of Cancerous Change
The progression of a tubular adenoma to cancer is a concern, but the overall likelihood is relatively low, with less than 10% of tubular adenomas becoming cancerous. Despite this low percentage, it is important to understand that approximately 95% of colorectal cancers develop from adenomas. Several factors influence the risk of a tubular adenoma transforming into cancer.
The size of the adenoma is a significant factor, with larger adenomas carrying a higher risk. For instance, very small adenomas have a low risk of becoming cancerous, while larger ones (over 20 millimeters) have a significantly higher risk. The degree of dysplasia, which refers to the severity of abnormal cell growth, also plays a role; adenomas with high-grade dysplasia have a greater potential for malignancy.
The presence of villous features increases the risk of cancerous change. Villous adenomas, characterized by long, finger-like projections, tend to be larger and have a higher malignant potential than purely tubular adenomas. The number of adenomas detected also affects the overall risk; individuals with multiple tubular adenomas may face a higher risk of developing colorectal cancer. For example, having three to ten tubular adenomas is associated with an increased risk compared to having one or two small ones.
Detection and Management
Tubular adenomas are detected through a colonoscopy, a procedure where a doctor uses a flexible tube with a camera to examine the inside of the colon and rectum. If tubular adenomas are found during this examination, they are removed through a procedure called polypectomy, often performed during the same colonoscopy. This removal is a management approach aimed at preventing their progression to cancer.
Following polypectomy, follow-up surveillance with repeat colonoscopies is recommended. The frequency is determined by the characteristics of the removed adenoma(s), such as their size, number, and degree of dysplasia. For example, less frequent surveillance is advised for small, low-risk adenomas, while larger, more numerous, or higher-grade adenomas require more frequent monitoring, often around 3 years. This ongoing monitoring helps to detect and remove any new polyps that may develop, further reducing the risk of colorectal cancer.