From polyps to cancer: Analyzing risk factors and the role of anatomical pathology

1. Risk factors for the development of colorectal polyps and colorectal cancer

Colorectal cancer (CRC) often develops from polyps, and this process may take several years [3, 4]. Risk factors associated with the development of colorectal polyps and colorectal cancer can be divided into the following main categories:

1.1. Non-modifiable risk factors

Age: The risk of colorectal cancer increases with age, with the average age at diagnosis of sporadic colon cancer being over 65 years [1, 3].
Sex: Men are more likely to develop colon cancer (53%) and are diagnosed at a younger age than women (68 versus 72 years) [3].
Family history and genetics: A family history of colorectal cancer or colorectal polyps increases the risk of developing the disease [1, 3]. Approximately 5% of colon cancer cases are attributable to inherited genetic mutations, primarily Lynch syndrome and familial adenomatous polyposis (FAP) [3].
Race: Colorectal cancer incidence and mortality rates are higher among African Americans and Alaska Native populations [3, 9].

1.2. Lifestyle and environmental factors

Diet: A diet low in fruits, vegetables, and fiber, high in fat, or rich in processed red meat increases the risk [1, 3].
Smoking and alcohol consumption: Tobacco use and alcohol consumption increase the risk of colorectal cancer [1, 3].
Obesity and physical inactivity: Being overweight or obese and engaging in insufficient regular physical activity may increase the risk [1, 3].
Radiation exposure: A history of previous radiation therapy is also a risk factor [3].

1.3. Underlying conditions and hereditary syndromes

Inflammatory bowel disease (IBD): Conditions such as Crohn's disease and ulcerative colitis may increase the risk of colorectal cancer [1, 3]. The annual incidence of cancer in patients with ulcerative colitis is estimated at 0.5% during the first 10–20 years after IBD diagnosis, increasing to 1% per year thereafter [3].
Hereditary polyposis syndromes:
- Familial adenomatous polyposis (FAP): An inherited condition that substantially increases the risk of developing polyps and colorectal cancer [1, 3].
- Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC): An inherited syndrome that increases the risk of colorectal cancer and several other cancers [1, 3].
- Peutz-Jeghers syndrome: Another hereditary syndrome associated with an increased risk of polyps and cancer [3].

2. Histopathological classification of colorectal polyps and cancer risk

Colorectal polyps are classified histopathologically into two main groups: non-neoplastic and neoplastic polyps [4, 6].

2.1. Non-neoplastic polyps

These polyps are generally benign and have a very low risk of malignant transformation [4, 6].

Hyperplastic polyps: Very common, usually found in the distal colon, and associated with a very low risk of malignancy [4].
Inflammatory polyps: Arise from inflammatory reactions in the intestinal mucosa [6].
Hamartomatous polyps (juvenile polyps): Benign growths commonly found in children and not considered precancerous [4].

2.2. Neoplastic polyps

These polyps have the potential to develop into cancer. More than 95% of colorectal adenocarcinomas originate from these polyps [4].

Adenomas: The most common type of neoplastic polyp and considered the precursor to most cases of colorectal cancer [4, 6].
- Tubular adenomas: The most common type, accounting for more than 80% of adenomas [4].
- Villous adenomas: Account for 5–15% of adenomas and carry a higher risk of malignant transformation [4, 6].
- Tubulovillous adenomas: Combine features of both tubular and villous adenomas and account for 5–15% of adenomas [4].
Sessile serrated polyps (SSPs): Commonly found in the proximal colon and have significant malignant potential, particularly when dysplasia is present [4].
Traditional serrated adenomas (TSAs): Less common, usually found in the distal colon, and have significant malignant potential [4].

2.3. Other histopathological factors affecting cancer risk

Degree of dysplasia: Adenomas exhibit varying degrees of dysplasia, ranging from low grade to high grade. High-grade dysplasia indicates an increased risk of malignant transformation over time [4, 6].
Polyp size and number: Cancer risk increases substantially with larger polyps, such as those greater than 1 cm, and with a greater number of polyps [4, 6].
Polyp location: Polyps in the proximal (right-sided) colon may carry a different risk from those in the distal (left-sided) colon [4].
Time required for adenoma-to-carcinoma progression: The progression from normal colonic epithelium to invasive cancer occurs through the accumulation of genetic changes over time [3].

3. The role of anatomical pathology in polyp management and cancer prevention

Anatomical pathology plays a central role in diagnosing colorectal polyps, assessing their risk, and guiding management, thereby making an important contribution to colorectal cancer prevention.

3.1. Definitive diagnosis and classification

Accurate diagnosis: After a polyp is removed endoscopically, the tissue specimen is sent to the pathology laboratory to determine the polyp type (neoplastic or non-neoplastic) and the degree of dysplasia [4, 7].
Assessment of invasion: A diagnosis of a malignant colorectal polyp (invasive cancer) requires tumor cells to invade through the muscularis mucosae into the submucosa [7].
Key reporting features: The pathological report for a malignant polyp should include important information such as the size of the invasive component, the presence of lymphovascular invasion, tumor differentiation, and the distance between the tumor and the resection margin [7]. These factors are closely associated with the risk of lymph node metastasis and recurrence [7].
Histological grading: Adenocarcinomas are graded according to the extent of gland formation as well differentiated (>95%), moderately differentiated (>50%), or poorly differentiated (<49%) [3, 7].

3.2. Guiding surveillance and treatment strategies

Treatment decisions: Pathology results help clinicians determine whether polypectomy alone is sufficient or whether the patient requires more extensive surgical resection [7].
Prognostic factors: Poor differentiation, lymphovascular invasion, positive resection margins, and high-grade tumor budding are adverse prognostic factors that may require more intensive intervention or closer surveillance [3, 7].
Molecular biology: Molecular biomarker tests, including KRAS and BRAF mutation testing and microsatellite instability (MSI) assessment, can provide important information for personalized treatment, particularly in metastatic colorectal cancer [3, 7].

3.3. Screening and surveillance after polypectomy

Colonoscopy schedule: Based on the pathology results of the removed polyp, the physician recommends the appropriate timing and frequency of follow-up colonoscopy [4]. For example, small distal hyperplastic polyps may not require surveillance as frequently as large adenomas with high-grade dysplasia [4].
Colonoscopy: This is the gold standard for detecting colorectal polyps and colorectal cancer [4, 8]. Polyps can be removed during the procedure, preventing them from progressing to cancer [8].

4. When should you see a doctor?

You should consult a doctor if you experience any of the following symptoms or belong to a high-risk group:

Unusual changes in bowel habits, such as persistent diarrhea or constipation [2, 8].
Blood in or on the stool [2, 8].
A feeling of incomplete bowel evacuation, unexplained abdominal pain, or cramping [2].
Unexplained weight loss [2].
Being 45 years of age or older, when regular colorectal cancer screening is recommended even in the absence of symptoms [8, 9].
A family history of colorectal polyps or colorectal cancer, or a hereditary syndrome associated with these conditions [1, 8].
A diagnosis of inflammatory bowel disease (IBD) [1, 8].

Medical evaluation and early screening are important for detecting and treating precancerous polyps or early-stage cancer in a timely manner, thereby increasing the likelihood of successful treatment [8].

5. Frequently asked questions (FAQ)

Do all colorectal polyps eventually develop into cancer? No. Not all colorectal polyps progress to cancer. Non-neoplastic polyps, such as hyperplastic and inflammatory polyps, are generally benign and have a very low risk of malignant transformation. However, neoplastic polyps, particularly adenomas and serrated polyps, can develop into cancer if they are not removed [4, 6].
Which types of polyps have the highest risk of malignant transformation? Polyps with the highest risk include villous adenomas, sessile serrated polyps with dysplasia, and traditional serrated adenomas. Larger polyp size and a higher degree of dysplasia also substantially increase this risk [4, 6].
Is colorectal polyp screening effective in preventing cancer? Yes. Colorectal polyp screening is highly effective in preventing colorectal cancer. Screening methods such as colonoscopy can detect and remove precancerous polyps before they have the opportunity to develop into cancer [8]. Regular screening significantly reduces colorectal cancer incidence and mortality [3, 9].
How can diet and lifestyle help reduce the risk of polyps and colorectal cancer? Maintaining a healthy lifestyle can reduce the risk. This includes eating a diet rich in fruits, vegetables, and fiber; limiting red and processed meat; maintaining a healthy weight; exercising regularly; avoiding tobacco use; and limiting alcohol consumption [1, 3].
If I have a family history of colorectal cancer, when should I start screening? People with a family history of colorectal cancer or colorectal polyps may need to begin screening earlier than the generally recommended starting age of 45 years [8, 9]. It is best to consult a doctor to determine an appropriate screening schedule based on family history and individual risk factors [8].

6. References

CDC (2024). Colorectal Cancer Risk Factors. https://www.cdc.gov/colorectal-cancer/risk-factors/index.html.
Mayo Clinic. Colon cancer - Symptoms and causes. https://www.mayoclinic.org/diseases-conditions/colon-cancer/symptoms-causes/syc-20353669.
Menon, G., & Cagir, B. (2025). Colon Cancer - StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK470380/.
Meseeha, M., & Attia, M. (2025). Colon Polyps - StatPearls. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK430761/.
Wickramasinghe, D. P., Samaranayaka, S. F., Lakmal, C., Mathotaarachchi, S., Kanishka Lal, C., Keppetiyagama, C., & Samarasekera, D. N. (2014). Types and Patterns of Colonic Polyps Encountered at a Tertiary Care Center in a Developing Country in South Asia. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC4333906/.
Colucci, P. M., Yale, S. H., & Rall, C. J. (2003). Colorectal Polyps. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC1069054/.
Geramizadeh, B., Marzban, M., & Owen, D. A. (2017). Malignant Colorectal Polyps; Pathological Consideration (A review). PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC5938718/.
CDC (2025). Screening for Colorectal Cancer. https://www.cdc.gov/colorectal-cancer/screening/index.html.
United States Preventive Services Task Force (2021). Recommendation: Colorectal Cancer: Screening. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/colorectal-cancer-screening.

The information above is for reference purposes only and is not intended as medical advice. Please contact your doctor for detailed medical consultation.