A polyp is a growth that protrudes from a mucous membrane, the moist tissue lining the inside of certain organs. Polyps can form in the colon, stomach, uterus, nose, and other areas where these membranes exist. Most polyps are benign, but some types can develop into cancer over time, which is why doctors take them seriously and often recommend removal.
How Polyps Look and Grow
Polyps come in two basic shapes. Pedunculated polyps hang from the tissue wall on a narrow stalk, like a mushroom. Sessile polyps sit flat against the membrane surface without a stalk. The distinction matters because sessile and flat polyps have less distance between their abnormal tissue and the deeper layers beneath, which can make cancer progression harder to catch early.
Polyps range from a few millimeters to several centimeters. Many are too small to cause symptoms and are discovered incidentally during routine exams or imaging done for other reasons.
Colon Polyps and Cancer Risk
The colon is the most well-known location for polyps, and the stakes are high: more than 95% of colon cancers originate from polyps. That said, not all colon polyps carry the same risk. The type matters enormously.
Adenomatous polyps are the primary concern. These are the ones that can develop into cancer if they grow and accumulate abnormal cell changes over time. A 1-centimeter adenomatous polyp has roughly an 8% chance of becoming cancerous within 10 years and a 24% chance within 20 years. The progression from a benign adenoma to cancer is slow, often taking up to 20 years, which is exactly why screening works so well.
Hyperplastic polyps are very common, especially in the lower colon, and carry very low cancer risk. These are the type most often found and removed without much concern.
Sessile serrated polyps are found more often in the upper colon. Without abnormal cell changes, their cancer risk is low. But if they develop dysplasia (cells that look increasingly abnormal under a microscope), the risk becomes significant.
Juvenile polyps are benign and not precancerous.
Stomach Polyps
Polyps in the stomach are usually found by accident during an upper endoscopy. The most common type, fundic gland polyps, account for 37% to 77% of all gastric polyps and occur most frequently in middle-aged women. They’re strongly linked to long-term use of proton pump inhibitors, the acid-reducing medications many people take for heartburn and reflux. One study found the risk of developing these polyps increased 17-fold after 10 years of PPI use.
Hyperplastic stomach polyps are the second most common type, making up 17% to 42% of cases. These are tied to chronic inflammation, particularly from H. pylori infection. They tend to shrink or disappear after treating the infection and reducing stomach acid. Gastric adenomas, the type with the highest cancer risk, are rare, representing less than 1% of stomach polyps.
Nasal Polyps
Nasal polyps develop in the lining of the nose and sinuses, driven by chronic inflammation lasting more than 12 weeks. Small ones cause no symptoms at all. Larger polyps or clusters can block airflow and lead to a stuffy nose, loss of smell and taste, postnasal drip, facial pressure, snoring, and recurrent sinus infections. Conditions like asthma and chronic allergies increase the risk, though researchers still don’t fully understand why some people develop nasal polyps and others with the same conditions don’t.
Uterine Polyps
Endometrial polyps grow from the lining of the uterus. Abnormal uterine bleeding is the most common symptom. Among women with irregular bleeding, 20% to 30% turn out to have endometrial polyps. They’re also frequently discovered during fertility evaluations. Most clinicians recommend removing uterine polyps before fertility treatments like IVF, since the polyps may interfere with embryo implantation. Removal is typically done through hysteroscopy, a minimally invasive procedure where a thin camera is inserted through the cervix to locate and remove the growth.
What Happens When a Polyp Is Found
During a colonoscopy or endoscopy, most polyps are removed on the spot using a snare, a thin wire loop that encircles the polyp and cuts it away from the tissue. For polyps under 10 millimeters, a cold snare technique (without electrical current) is preferred because it lowers the risk of bleeding and complications. Larger or more complex polyps may require techniques that lift the tissue with an injection before removal.
Once removed, the polyp is sent to a lab where a pathologist examines it under a microscope. This is the only way to determine the polyp’s type and whether any cells show precancerous or cancerous changes. Your follow-up schedule, including when you’ll need your next colonoscopy, depends largely on what the lab report shows.
Screening Recommendations
The U.S. Preventive Services Task Force recommends colorectal cancer screening starting at age 45 for adults at average risk. Screening is most strongly recommended for adults between 50 and 75. “Average risk” means no personal or family history of colorectal cancer, adenomatous polyps, inflammatory bowel disease, or genetic syndromes that raise cancer risk. If you have any of those factors, screening typically starts earlier.
Genetic Conditions That Cause Polyps
Some people are genetically predisposed to develop large numbers of polyps. Familial adenomatous polyposis (FAP) is caused by mutations in the APC gene and leads to hundreds or even thousands of colon polyps. In the classic form, polyps begin appearing in childhood, and by age 35, 95% of affected individuals have them. Without treatment, one or more of these polyps will almost certainly become cancerous. An attenuated form of FAP produces fewer polyps (around 30 on average) that appear later, in early to mid-adulthood, but still carries elevated cancer risk.
Lynch syndrome is another inherited condition that increases the risk of colon polyps and several other cancers. People with a strong family history of colorectal cancer, especially at young ages, are often tested for these genetic conditions so that screening and prevention can begin early.