Polyps are abnormal growths on the inner lining of the colon. While many are harmless, tubular adenomas are a common type of colon polyp considered precancerous. They indicate an increased risk for colorectal cancer, highlighting the importance of their detection and management.
Understanding Tubular Adenomas
Tubular adenomas are benign growths originating from the glandular tissue lining the colon or rectum. These polyps are characterized by a tubular microscopic structure. They are the most common type of adenomatous polyp, accounting for approximately 65% to 80% of all adenomas found during colonoscopies.
Tubular adenomas are considered precancerous because they have the potential to develop into adenocarcinoma, a type of colorectal cancer, over time if left untreated. While around 50% of the population may develop tubular adenomas, fewer than 10% of them actually become cancerous. These polyps are typically small, with about 90% measuring less than 1 centimeter in diameter, and can be found anywhere in the large intestine.
Under a microscope, tubular adenomas display dysplastic or abnormal cells. This abnormality is classified as either low-grade or high-grade dysplasia. Low-grade dysplasia indicates mildly abnormal cells that are still relatively organized, carrying a very low risk of cancer. High-grade dysplasia, however, signifies more abnormal and less organized cells, indicating a higher chance of progression to colorectal cancer.
Detection and Diagnosis
The primary method for detecting tubular adenomas is a colonoscopy. During this procedure, a thin, flexible tube with a camera, called a colonoscope, is inserted through the rectum to visualize the colon’s inner lining. This allows a gastroenterologist to identify any abnormal growths, such as polyps.
Other screening methods, like fecal immunochemical tests (FIT) or stool DNA tests, can indicate the possible presence of polyps by detecting blood or abnormal DNA in stool samples. However, these tests primarily identify the need for a colonoscopy, which is then performed for both diagnosis and removal of any detected polyps.
Once a polyp is visually identified during a colonoscopy, a biopsy is performed. This sample is then sent for pathological examination. A pathologist analyzes the tissue to confirm the type of polyp, assess the degree of dysplasia, and determine if the polyp was completely removed or shows any signs of cancerous invasion.
Management and Follow-up
The standard approach to managing tubular adenomas involves their removal, typically performed during the same colonoscopy in which they are detected. This procedure, known as a polypectomy, is performed using a retractable wire loop or forceps to detach the adenoma from the colon’s lining. For smaller polyps, a special device that delivers heat may be used to destroy them.
Removing these precancerous polyps is necessary to prevent their progression into colorectal cancer. The removed tissue is sent for microscopic examination to confirm the polyp’s characteristics and ensure complete removal.
Surveillance colonoscopies are conducted after tubular adenoma removal to monitor for new polyps or recurrence, with frequency depending on the number, size, and grade of dysplasia of the removed adenomas. For instance, individuals with one or two small tubular adenomas (less than 10 mm) with low-grade dysplasia may need a follow-up colonoscopy in 7 to 10 years. If three to four small tubular adenomas are found, the interval may be shortened to 3 to 5 years. Larger adenomas (10 mm or greater), or those with high-grade dysplasia, often warrant a repeat colonoscopy in approximately 3 years.
Risk Factors and Prevention Strategies
Several factors can increase an individual’s risk of developing tubular adenomas. Age is a factor, with the risk increasing after 50 years old. A personal or family history of polyps or colorectal cancer elevates the risk. Certain inherited genetic conditions, such as familial adenomatous polyposis (FAP), are associated with a higher likelihood of developing these polyps.
Lifestyle choices play a role in the development of tubular adenomas. Obesity, a diet high in red and processed meats, and a lack of physical activity are contributing factors. Smoking and heavy alcohol consumption have been linked to an increased risk of colorectal polyps and cancer. Inflammatory bowel diseases are recognized as a risk factor.
To mitigate the risk of developing tubular adenomas and colorectal cancer, lifestyle modifications are recommended. Adopting a diet rich in fruits, vegetables, and whole grains, while limiting red and processed meats, is beneficial. Regular physical activity and maintaining a healthy body weight are preventative measures. Avoiding smoking and limiting alcohol intake are steps to reduce risk. Regular colorectal cancer screening, primarily through colonoscopy, is a primary prevention method, allowing for early detection and removal of polyps before they become cancerous.