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Intestinal Adenomatous Polyps

  • Writer: FibonacciMD
    FibonacciMD
  • Jun 2
  • 5 min read

Updated: Jun 2

Understanding Adenomatous Polyps as Precursors to Colorectal Cancer

Adenomatous polyps are common precancerous lesions linked to colorectal cancer and frequently detected through colonoscopies. This post explores their causes and risk factors, histology, diagnostic screening, and follow-up detection to reduce cancer risk.


Adenomatous polyps
Adenomatous Polyp

By  Devon Drew, Nancy Mills, and Richard Strongwater


Adenomatous polyps are dysplastic lesions resulting from APC gene mutation that cause increased intestinal crypt cell proliferation. They are considered to be precancerous and are the precursor lesions to ~70% of colorectal cancers. They are the most common finding in screening colonoscopies, with a prevalence of ~30% in average-risk individuals. Typically, these polyps are asymptomatic and discovered only on routine colonoscopy, but they may cause bleeding.


Adenomatous polyps that are small and contain only low-grade dysplasia have limited clinical significance, but they are nonetheless removed to prevent the possibility of progression to cancer. Such progression is believed to take ~10 years. The risk of progression is low in non-advanced lesions < 5 mm in size; it is present in < 1% of lesions 6-9 mm in size.


Causes and Risk Factors

Increasing age, male gender, family history of colon cancer, family history of advanced adenomatous polyps, and inherited polyposis syndromes increase the risk of developing adenomatous colon polyps.


Diagnostic Evaluation

Colonoscopy is the gold standard for discovering adenomatous polyps. It has a high sensitivity for their detection. Polyps are removed and sent to pathology for further evaluation.


Upon microscopic evaluation, adenomatous polyps can be subclassified into tubular, villous, or tubulo-villous types, depending on their histology. The majority are tubular, but if they contain > 25% villous architecture, they are then designated tubulo-villous; > 75% villous architecture classifies them as villous. Most lesions contain only low-grade dysplasia, but increasing lesion size increases the likelihood of finding invasive cancer or villous elements within the lesion. Adenomatous polyps > 1 cm in size or containing high-grade dysplasia and/or villous elements are considered to be advanced; these carry a higher risk of progression to cancer. Polyps may also be classified as elevated, flat, or depressed, depending on their morphology. A depressed morphology increases the likelihood of adenocarcinoma occurrence even in smaller lesions.


Computed tomography colonography and capsule colonoscopy have a high sensitivity for the detection of adenomatous polyps > 1 cm in size but less sensitivity than traditional colonoscopy for small polyps. Additionally, patients with polyps measuring > 6 mm that are found during these procedures are advised to undergo traditional colonoscopy for polyp removal. Fecal immunochemical testing (FIT), FIT-fecal DNA testing (see below), flexible sigmoidoscopy, and Septin9 screening are additional tests that aid in the detection of colorectal cancer but that have limited utility in the detection of precancerous adenomatous polyps.


Treatment and Recommended Follow-Up

Screening colonoscopy or other detection methods should begin at age 45 in average-risk individuals. All polyps are endoscopically or surgically removed upon detection. However, depending on the size and morphology of the polyp, complete resection may not always be achieved. Between 19%–27% of colorectal cancer that occurs between colonoscopy screenings appear at the site of a previously removed polyp where residual tissue has been left behind.


Generally, patients with no polyps may undergo follow-up colonoscopy at 10-year intervals if not considered high risk. Individuals having 1–2 tubular adenomas < 10 mm in size are considered to be at low risk, and the recommended follow-up colonoscopy can be performed in 5-10 years. Individuals having either adenomas containing villous architecture, polyps > 10 mm in size, three or more adenomas, or high-grade dysplasia are considered to be at high risk and should be followed up with colonoscopy in 3 years.

Individuals with a relative who had colorectal cancer or advanced/high risk polyps are at higher risk and should be screened with colonoscopy beginning at age 40 or 10 years younger than the age of the relative at diagnosis. If the relative was < 60 years of age, the screening should occur every 5 years; it should occur every 10 years if the relative was older than 60.




CDC

Screening recommendations


The US Preventive Services Task Force (Task Force) www.UsPreventiveServicesTaskForce.org  recommends that adults age 45 to 75 be screened for colorectal cancer. The decision to be screened between ages 76 and 85 should be made on an individual basis. For patients at an increased risk of getting colorectal cancer, screening should be made on an individual basis- considering when to begin screening, which test is right for them, and how often to be tested.

Most patients should begin screening for colorectal cancer soon after turning 45, then continue screening at regular intervals. However, the patient may need to be tested earlier than 45, or more often than other people, if they have:


Stool tests

  • The guaiac-based fecal occult blood test (gFOBT) uses the chemical guaiac to detect blood in the stool. It should be done once a year. 

  • The fecal immunochemical test (FIT) aka iFOBT checks for blood generally from the lower intestines and uses antibodies to detect for blood in the stool. It is also done once a year in the same way as a gFOBT. Unlike the guaiac-based fecal occult blood test (gFOBT), the FIT test does not have any drug or dietary constraints because vitamins and foods do not affect the test outcome. 


Multitargeted stool DNA or RNA tests with fecal immunochemical testing (FIT) look for certain abnormal sections of DNA or RNA from cancer or polyp cells, as well as for occult blood. Colorectal cancer or polyp cells often have DNA or RNA mutations.

  • The FIT-DNA test (also referred to as the stool DNA test) combines the FIT with a test that detects altered DNA in the stool. For this test, you collect an entire bowel movement and send it to a lab, where it is checked for altered DNA and for the presence of blood. It is done once every 3 years. The Cologuard brand tests for DNA changes and for blood in the stool.

  • ColoSense tests for RNA changes and blood in the stool. It is currently approved by the FDA but not yet by the American Cancer Society or the US Preventive Services Task Force (USPSTF). Insurance coverage is not universal.


Insurance and Medicare coverage

Colorectal cancer screening tests may be covered by your health insurance policy without a deductible or co-pay. For more information about Medicare coverage, visit www.medicare.gov or call 1-800-MEDICARE (1-800-633-4227). TTY users should call 1 (877) 486-2048. Check with your insurance plan to find out what benefits are covered for colorectal cancer screening.


📘 More to Read


Early-Onset Colorectal Cancer on the Rise

More young adults are being diagnosed with colorectal cancer, a trend that has experts concerned. Staying informed is crucial—for patients, families, and healthcare professionals alike.


🎓Continuing Medical Education (CME) Opportunity

Free CME for Medical Professionals

Healthcare providers: Stay current on the rising incidence of early-onset colorectal cancer.

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Sources:

  • Hamilton SR, Aaltonen LA, eds. World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Digestive System. Lyon, France:IARC Press; 2000:111-112.

  • Heitman SJ, Ronksley PE, Hilsden RJ, Manns BJ, Rostom A, Hemmelgarn BR. Prevalence of adenomas and colorectal cancer in average risk individuals: a systematic review and meta-analysis. Clin Gastroenterol Hepatol. 2009;7:1272-1278.

  • Lieberman DA, Rex DK, Winawer SJ, Giardiello FM, Johnson DA, Levin TR. Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology. 2012;143:844-857.

  • Rex DK, Boland CR, Dominitz JA, et al. Colorectal cancer screening: recommendations for physicians and patients from the U.S. Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol. 2017;112:1016-1030.

  • Colorectal Cancer Screening Tests. American Cancer Society. Feb 28,2025. https://www.cancer.org › detection-diagnosis-staging

  • Screening for Colorectal Cancer. Centers for Disease Control and Prevention. Oct 17, 2024. https://www.cdc.gov › colorectal-cancer › screening

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