Colon polyps are growths that form on the inner lining of the large intestine (colon or rectum). These growths are extremely common, and while most are benign, many colorectal cancers begin as a polyp. Colorectal cancer is highly preventable when these precursor lesions are detected and removed early.
What Colon Polyps Are and Where They FormColon polyps arise from the mucosal membrane lining the large intestine and can appear anywhere from the cecum to the rectum. Polyps vary widely in size, ranging from a few millimeters (diminutive) to several centimeters.
Polyps are broadly categorized into two main shapes: sessile and pedunculated. A pedunculated polyp resembles a mushroom, hanging from the colon wall by a thin stalk. In contrast, a sessile polyp is dome-shaped and grows directly against the colon wall without a stalk.
Sessile polyps are the more common shape. A third, less common shape is the flat polyp, which is flush or slightly depressed into the colon lining. Polyps typically appear smooth or lobulated, and their color is similar to the surrounding mucosal tissue.
Classifying Polyps by Appearance and RiskPolyp classification is based on cellular structure, which determines the potential to become cancerous. The main distinction is between adenomatous polyps (adenomas) and non-adenomatous polyps. Adenomas are considered pre-cancerous lesions because most colorectal cancers develop from this type.
The cancer risk of an adenoma relates to its size and internal growth pattern (histology). Tubular adenomas, which he a tube-like structure, are the most common and carry a lower risk of malignancy. Villous adenomas he a sprawling structure, are typically larger, and carry a higher risk of progressing to cancer. Tubulovillous adenomas display a mix of both growth patterns.
Non-adenomatous polyps include hyperplastic and inflammatory polyps. Hyperplastic polyps are low-risk and benign. However, sessile serrated lesions (SSLs) look similar but he a distinct “saw-tooth” appearance and carry a significant cancer risk, requiring treatment similar to adenomas.
The progression from a normal cell to a cancerous tumor is described by the adenoma-carcinoma sequence. This pathway involves genetic mutations causing cells to become disorganized, a process termed dysplasia. Low-grade dysplasia suggests mild abnormality, while high-grade dysplasia indicates cells are highly abnormal and closer to becoming cancerous.
Why Early Detection is VitalFinding small, pre-cancerous polyps is the core goal of screening, as they rarely cause symptoms early on. Since polyps take many years to transform into cancer, screening provides a wide window for effective intervention and prevention.
The gold standard for detection and prevention is the colonoscopy, which allows a physician to visually inspect the entire large intestine. During the procedure, the physician can remove any discovered polyps immediately, making it the most comprehensive option.
Other screening methods offer non-invasive alternatives for erage-risk individuals. The Fecal Immunochemical Test (FIT) is a stool test that looks for hidden blood shed by polyps or cancers. The multitarget stool DNA test checks for blood and detects abnormal DNA biomarkers released from lesions.
Virtual colonoscopy (CT colonography) uses an advanced X-ray scan to create 3D images of the colon. While it detects polyps, it is a diagnostic tool; if a polyp is found, a standard colonoscopy is still required for removal. A positive result from any alternative screening method typically leads to a follow-up colonoscopy.
Procedures for Removal and Post-Procedure CareThe removal of a colon polyp, called a polypectomy, is usually performed during a standard colonoscopy. For small polyps, a wire loop (snare) is passed through the endoscope, looped around the base, and used to cut the polyp off, often with an electric current to cauterize the tissue. Larger or flatter polyps may require removal in multiple pieces (piecemeal resection).
Once removed, the polyp is sent to a pathology lab for microscopic analysis. The pathologist determines the exact type of polyp (e.g., tubular adenoma or sessile serrated lesion) and checks for high-grade dysplasia or cancer cells. This report determines the patient’s future risk and the schedule for subsequent surveillance.
Post-polypectomy care is generally straightforward, with most patients resuming normal activities the next day. Patients monitor for rare complications like significant bleeding or severe abdominal pain. The most important element of post-procedure care is establishing a surveillance plan for follow-up colonoscopies.
The surveillance schedule is based on the number, size, and specific type of polyps removed. A patient with a single, small, low-risk adenoma might he a follow-up in five to ten years. Conversely, a patient with multiple polyps or a large polyp with high-risk features (like villous histology) requires a shorter surveillance interval, often three years.