A colon polyp is a small growth on the inner lining of the large intestine. While many are harmless, some types have the potential to change over time. Tubular adenomas are a common type of these growths found in the colon.
Understanding Tubular Adenomas
Tubular adenomas are a specific type of polyp. When viewed under a microscope, their cells form tube-like glands, which gives them their “tubular” designation. They are a common form of adenomatous polyp, accounting for about 80% of all adenomas removed during colonoscopies.
These growths can appear in various parts of the colon and rectum. They are often described as small, typically less than 1.25 cm (0.5 inch) in diameter. Tubular adenomas can be either pedunculated, meaning they grow on a stalk, or sessile, appearing as a flatter, slightly raised lump with a broad base.
Although tubular adenomas are generally small, their size can vary. The presence of tubular adenomas often goes unnoticed as they typically do not cause any symptoms.
Why Tubular Adenomas Matter
Tubular adenomas are considered precancerous lesions, signifying their potential to develop into colorectal cancer over time. While not cancerous themselves, these polyps can undergo changes that lead to the formation of a malignant tumor, known as an adenocarcinoma.
The development of colorectal cancer often follows a sequence where normal colon lining cells transform into adenomas, which can then progress to cancer. This process, termed the “adenoma-carcinoma sequence,” highlights the importance of identifying and removing adenomas before they become cancerous. Though only a small percentage, around 5% to 10%, of adenomas may become cancerous, approximately 95% of colorectal cancers originate from adenomas. Removing tubular adenomas effectively interrupts this progression, thereby preventing cancer development.
The risk of a tubular adenoma becoming cancerous increases with its size and the presence of more abnormal cellular changes. Larger polyps, those exceeding 1 cm (0.4 inch), and those exhibiting high-grade dysplasia (more severe cellular abnormalities) carry a higher likelihood of malignant transformation. Early detection and management are important for reducing the overall risk of colorectal cancer.
Detection and Management
Tubular adenomas are primarily detected through screening colonoscopy, which is considered the gold standard for identifying these growths. During a colonoscopy, a flexible tube with a camera is inserted into the colon, allowing a healthcare provider to visualize the inner lining and identify any polyps. This procedure offers the advantage of both detection and immediate removal of polyps.
When a tubular adenoma is found, it is typically removed during the same colonoscopy procedure. Small polyps can be removed using a wire loop or forceps, while larger ones might require specialized endoscopic techniques. After removal, the polyp tissue is sent to a laboratory for microscopic examination by a pathologist, who determines its type and checks for any signs of cancerous cells.
Following the removal of tubular adenomas, ongoing surveillance through repeat colonoscopies is recommended. The frequency of these follow-up examinations depends on several factors, including the number of adenomas found, their size, and the degree of cellular abnormality (dysplasia). For instance, individuals with one or two small tubular adenomas with low-grade dysplasia might need a repeat colonoscopy in 7 to 10 years. However, if multiple adenomas were present, or if any were larger than 1 cm (0.4 inch) or showed high-grade dysplasia, a shorter follow-up interval, often around 3 years, is typically advised. These surveillance guidelines help ensure that any new or recurring polyps are identified and removed promptly, further reducing the risk of colorectal cancer.