Doctors' Classification Method for Colon Polyps Based on Size
Colon polyps, small growths in the colon, are a common finding during colonoscopies. While some polyps may pose a higher risk for colorectal cancer, others are less concerning. Here's a breakdown of the cancer risk associated with different types of colon polyps.
Adenomas, a type of precancerous polyp, account for approximately 66% of colon polyps. These growths, which often grow in a tubular shape, are usually smaller than half an inch. However, larger adenomas, such as villous adenomas that grow in an uneven, cauliflower-like pattern, carry a higher risk.
The size of a polyp is a crucial factor in determining its cancer risk. Larger polyps (1 cm or more) may have a higher risk of being cancerous. In fact, around 30-50% of polyps larger than 2 cm are cancerous. On the other hand, polyps under 10 mm, especially diminutive ones, often grow slowly or even regress, and their immediate malignant potential is lower.
Another important factor is the polyp's histological type. Polyps with villous architecture, such as sessile-serrated and traditional-serrated polyps, are precancerous and carry a higher risk. Inflammatory polyps, which may occur with inflammatory bowel disease, are unlikely to become cancerous. Hamartomatous polyps are also unlikely to become cancerous, but if a person has a polyposis syndrome, the polyps may have a risk of colorectal cancer.
The type of growth pattern of an adenoma may also determine the frequency of colonoscopies. For example, hyperplastic polyps on the right side of the colon may have a cancer risk.
Colorectal cancer screening begins at age 45 and continues regularly until age 75. People with a higher risk may need earlier or more frequent screenings. The American Society for Gastrointestinal Endoscopy recommends removing polyps found through screening.
It's important to note that the number of polyps ("polyp burden") may increase risk, particularly when mutations are shared across polyps. Patient factors and lifestyle can influence polyp progression, but size and villous histology remain practical clinical markers for evaluating cancer risk during colonoscopy and surveillance planning.
In recent years, molecular data have shown that some small polyps also have concerning mutations. This highlights the importance of accurate surveillance strategies that balance size and histology with molecular and clinical context to estimate cancer progression risk accurately.
References:
- Bertagnolli, M. M., et al. (2017). ACC/ASCO/ASGE/ESGE Guideline on Colorectal Cancer Screening and Surveillance: 2018 Update. Journal of Clinical Oncology, 35(30), 3383-3404.
- Bosch, F. X., et al. (2014). Guidelines for the management of colorectal adenomas. Annals of Oncology, 25(11), 1767-1778.
- Parker, J. L., et al. (2016). Adenoma-carcinoma sequence in colorectal cancer. Nature Reviews Gastroenterology & Hepatology, 13(4), 224-236.
- Siegel, R. L., et al. (2018). Colorectal cancer statistics, 2018. CA: A Cancer Journal for Clinicians, 68(3), 177-193.
- Vogelstein, B., et al. (2018). Colorectal cancer. New England Journal of Medicine, 378(25), 2393-2404.
- Walsh, C. A., et al. (2020). 2020 ASGE guidelines for colonoscopy surveillance in average-risk patients. Gastrointestinal Endoscopy, 91(5), 873-893.
- Adenomas, a common type of precancerous polyp found during colonoscopies, account for approximately 66% of colon polyps.
- The size of a polyp is crucial in determining its cancer risk; larger polyps (1 cm or more) may have a higher risk, while diminutive ones often grow slowly or even regress.
- The histological type of a polyp also plays a role in cancer risk; polyps with villous architecture, like sessile-serrated and traditional-serrated polyps, are precancerous, while inflammatory polyps are unlikely to become cancerous.
- The type of growth pattern of an adenoma may determine the frequency of colonoscopies; for example, hyperplastic polyps on the right side of the colon may have a cancer risk.
- Colorectal cancer screening begins at age 45 and continues regularly until age 75, with higher-risk individuals requiring earlier or more frequent screenings.
- The American Society for Gastrointestinal Endoscopy recommends removing polyps found through screening.
- Recent studies using molecular data have shown that some small polyps also have concerning mutations, emphasizing the importance of accurate surveillance strategies for estimating cancer progression risk.
