As a general rule, the larger the adenoma, the more likely it is to eventually become a cancer. As a result, large polyps (larger than 5 millimeters, approximately 3/8 inch) are usually removed completely to prevent cancer and for microscopic examination to guide follow-up testing.
The size of a polyp typically does make a difference. The larger the polyp becomes, the bigger the risk of it developing into colon cancer. That risk increases significantly if the polyp is greater than 10 mm (1 cm); research has shown the larger a colon polyp becomes, the more rapidly it grows.
Large polyps are 10 millimeters (mm) or larger in diameter (25 mm equals about 1 inch).
A consensus of multiple national medical societies, however, recommends immediate polypectomy for all polyps 6 mm or larger (5).
Polyps can range in size from the less-than-5-millimeter “diminutive” category to the over-30-millimeter “giants.”
In 1 to 7 years, depending on a variety of factors: The number, size and type of polyps removed; if you have a history of polyps in previous colonoscopy procedures; if you have certain genetic syndromes; or if you have a family history of colon cancer.
Most polyps are benign (not cancerous). Your doctor can tell if a colon polyp is cancerous during a colonoscopy by collecting tissue to biopsy. The results of the biopsy are typically sent to your doctor within a week. Only 5% to 10% of all polyps become cancerous.
The risk of polyps smaller than 5 millimeters (mm) being cancerous is very low. In larger polyps, the risk of cancer increases. Colon polyps grow very slowly and often do not cause symptoms. Regular colon cancer screenings can help detect them before they become cancerous.
The doctor will then send any removed polyps to a pathologist for a biopsy to see if cancer is present. If the biopsy reveals that cancer is present, then cancer specialists will outline a treatment plan for the person. Common treatments for colon cancer include surgery, chemotherapy, and radiotherapy.
Most polyps grow slowly and take from between 10 and 15 years to become cancerous. Due to this general time frame, most screenings are scheduled every 10 years which gives Colorectal Surgical Associates time to remove any polyps before they become cancerous.
Nonneoplastic polyps include hyperplastic polyps, inflammatory polyps and hamartomatous polyps. Nonneoplastic polyps typically do not become cancerous. Neoplastic polyps include adenomas and serrated types. These polyps have the potential to become cancer if given enough time to grow.
Most polyps are benign (not cancerous). “However, many polyps are precancerous [adenomas], which, if they remain in place for over 5 to 7 years, may progress towards a cancer,” says Yale Medicine's Harry Aslanian, MD, a Yale Medicine gastroenterologist.
Some types of colon polyps are more likely to become cancerous than others. A doctor who specializes in analyzing tissue samples (pathologist) will examine your polyp tissue under a microscope to determine whether it is potentially cancerous.
Polyps are usually less than 1cm in size, although they can grow up to several centimetres. There are various forms: some are a tiny raised area or bulge, known as a sessile polyp. some look like a grape on a stalk, known as a pedunculated polyp.
Villous Adenoma (Tubulovillous Adenoma)
Approximately 15 percent of polyps detected in colon cancer screening are villous or tubulovillous adenomas. This type of polyp carries a high risk of turning cancerous.
After a colonoscopy, eat foods that are soft and easy to digest to ease side effects such as bloating or gas. This may include eggs, white toast, and applesauce for breakfast. For lunch or dinner, choices could include lean chicken without skin, mashed potatoes, and soft-cooked carrots.
A polypectomy lasts about 30 to 60 minutes and is an outpatient procedure, allowing patients to return home the same day. They should be back to a normal routine as soon as the next day.
Common Symptoms of Colon Polyps
Changes in Bowel Movements – Sometimes colon polyps can lead to constipation or diarrhea that persists for longer than a week, as well as general changes in bowel habits.
However, over time polyps can become large and malignant if they aren't treated. Many polyps are found to be pre-cancerous, which means they have the potential to turn cancerous if they aren't removed. With early detection through an endoscopic test, the risk can be eliminated by your gastroenterologist.
Approximately 1% of polyps with a diameter less than 1 centimeter (cm) are cancerous. More than one polyp or a polyp that is 1 cm or bigger places you at higher risk for colon cancer. Up to 50% of polyps greater than 2 cm (about the diameter of a nickel) are cancerous.
Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Some types of polyps can change into cancer over time (usually many years), but not all polyps become cancer. The chance of a polyp turning into cancer depends on the type of polyp it is.
They can occur anywhere in the large intestine or rectum, but are more commonly found in the left colon, sigmoid colon, or rectum.