- Clinical science
Colonic polyps are abnormal colonic mucosal overgrowths. They are a common finding in people over the age of 50. In rare cases, they may be seen in younger individuals as part of hereditary polyposis syndromes (e.g., familial adenomatous polyposis, Peutz‑Jeghers syndrome, etc.). On macroscopic examination, colonic polyps are either pedunculated (with a stalk) or sessile (without a stalk). Histologically, colonic polyps are most commonly adenomas (∼ 70%), followed by hyperplastic polyps, and, rarely, serrated polyps and hamartomatous polyps. Colonic polyps may be benign or have malignant potential. Adenomas have the highest malignant potential (5%) and most colonic carcinomas arise from them (adenoma‑carcinoma sequence). Most patients are asymptomatic, but they may present with altered bowel habits, blood/mucus in stool, and iron deficiency anemia. Colonoscopy is the diagnostic modality of choice, since it allows for direct visualization of the polyps, biopsy, and therapeutic snare polypectomy (of pedunculated polyps) or endoscopic submucosal resection (of sessile polyps). Large polyps (> 2 cm) or malignant polyps require surgical resection.
- Incidence increases with age: ∼ 30% of individuals > 50 years .
- Sex: ♂ > ♀
Epidemiological data refers to the US, unless otherwise specified.
|Malignant potential||Histological type||Subtypes||Characteristics|
|Low malignant potential|| |
|Mucosal polyps|| |
|Submucosal polyps|| |
|Moderate malignant potential||Serrated polyps||Hyperplastic polyps Hyperplasia of normal cellular components and sawtooth/serrated pattern of crypt epithelium|
|Sessile serrated polyps Morphology similar to hyperplastic polyps|
|Traditional serrated adenoma Serrated architecture with dysplasia|| |
|High malignant potential||Adenomatous polyps||Tubular adenoma Histology: proliferating cells form tubules|
|Tubulovillous adenoma Histology: Mixture of tubular and villous histological picture|| |
|Villous adenoma Histology: finger-like projections lined by dysplastic epithelium|
- Adenomatous polyposis syndromes
- Hamartomatous polyposis syndromes
Adenomatous polyposis syndromes
- Occurs in one in 10,000–30,000 live births
- < 1% of colorectal cancers in the U.S. are due to FAP
- Both sexes equally affected
- Polyposis typically develops within the third decade of life
- Clinical features
- Flexible sigmoidoscopy/colonoscopy: > 100 polyps are typically detected in the classic FAP 
- Genetic testing: detection of germline mutations in the APC gene establishes the diagnosis 
- Histology: tubular, tubulovillous, and villous adenomas
- Prognosis: The lifetime risk of colorectal cancer is 100% by 45 years of age.
Variants of FAP
- Attenuated FAP
- Gardner syndrome
- Turcot Syndrome
- Autosomal dominant
- New mutations: 20% of cases
- Clinical features: 95% of patients have mucocutaneous hyperpigmentation that typically affects the lips (perioral lentigines), buccal mucosa, palms, and soles
- Enteroscopy: multiple hamartomatous polyps throughout the gastrointestinal tract
- Etiology: autosomal dominant with incomplete penetrance
- Clinical features: Onset is within the first decade of life, often with gastrointestinal bleeding and anemia
- Colonoscopy: > 10 polyps throughout the gastrointestinal tract
- Etiology: autosomal dominant
- Multiple GI polyps + skin manifestations such as papules and hyperkeratosis of the skin and mucous membranes
- Changes in the thyroid and mammary glands: > 50% of patients have thyroid disorders (e.g., multinodular goiter, adenomas, etc.) and benign breast disorders (e.g., fibroadenomas, intraductal papillomas, etc.).
- Etiology: : probably immune-mediated (rare, nonfamilial disorder)
- Clinical features: GI polyposis with alopecia and cutaneous hyperpigmentation
- Treatment: immune suppression with glucocorticoids and azathioprine
- Laboratory tests
- Advantage: does not require extensive bowel preparation before the procedure.
- Disadvantage: The rest of the colon is not visualized.
- Colonoscopy (confirmatory test)
Treatment depends on the etiology and nature of the polyp or polyps.
- Snare polypectomy: of pedunculated polyps (< 2 cm in size)
- Endoscopic mucosal resection: large sessile polyps
- Surgical resection
- For follow‑up, see .