• Clinical science

Colonic polyps

Abstract

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.

Epidemiology

  • Incidence increases with age: ∼ 30% of individuals > 50 years .
  • Frequency
  • Sex: >

References:[1][2][3]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

  • The exact etiology is unknown.
  • Risk factors

References:[4]

Classification

Malignant potential Histological type Subtypes Characteristics
Low malignant potential

Hamartomatous polyps

.

Juvenile polyposis syndrome

Peutz-Jeghers syndrome

Cowden syndrome

Cronkhite-Canada syndrome

Inflammatory polyps (pseudopolyps)
Mucosal polyps
  • Benign
  • Typically small < 5 mm
Submucosal polyps
  • Benign
  • Submucosal lipoma (most common)
Moderate malignant potential Serrated polyps Hyperplastic polyps Hyperplasia of normal cellular components and sawtooth/serrated pattern of crypt epithelium
  • Minimal risk of malignancy
  • Small (< 5 mm)
  • Common in distal colon (rectosigmoid)
Sessile serrated polyps Morphology similar to hyperplastic polyps
  • Risk of malignancy: ∼ 5%
  • Sessile lesions
  • > 5 mm in size
  • Common in proximal colon (ascending colon)
Traditional serrated adenoma Serrated architecture with dysplasia
  • Risk of malignancy: ∼ 5%
  • Common in rectosigmoid
High malignant potential Adenomatous polyps Tubular adenoma Histology: proliferating cells form tubules
  • Risk of malignancy: < 5%
  • Frequency: ∼ 80%
  • Location: anywhere in the colon
Tubulovillous adenoma Histology: Mixture of tubular and villous histological picture
  • Risk of malignancy: ∼ 20%
  • Frequency: 5–15%
Villous adenoma Histology: finger-like projections lined by dysplastic epithelium
  • Risk of malignancy: ∼ 50%
  • Frequency: 5–15%
  • Location: common in the rectum
  • Larger than other adenomas (cauliflower-like), and often sessile.


The majority of colon carcinomas develop from adenomas (adenoma‑carcinoma sequence). However, only ∼ 5% of adenomas develop into colon cancers!

Although villous adenoma is rarer than tubular adenoma, it has the highest malignant potential!

References:[1][2][5][6][7]

Clinical features

  • Mostly asymptomatic
  • If symptomatic
    • Blood in stool (hematochezia) is the most common symptom.
    • Change in bowel habits (constipation/diarrhea)
    • Mucus in stool
  • Physical examination

References:[1]

Subtypes and variants

Hereditary polyposis syndrome

  • Adenomatous polyposis syndromes
  • Hamartomatous polyposis syndromes

Adenomatous polyposis syndromes

Familial adenomatous polyposis (FAP)

Primarily hamartomatous

Peutz-Jeghers syndrome

  • Inheritance
  • Clinical features: 95% of patients have mucocutaneous hyperpigmentation (e.g., lips (perioral lentigines), buccal mucosa, palms, and soles)
  • Enteroscopy: < 20 polyps, primarily in the jejunum
  • Prognosis

Juvenile polyposis syndrome (JPS)

Cowden syndrome

Cronkhite-Canada syndrome

MUTYH‑associated polyposis

References:[2][8][9][10][11][12][13][14][15]

Diagnostics

  • Laboratory tests
  • Imaging
    • Virtual colonoscopy:
    • Air contrast barium enema: can detect left-sided colonic polyps
  • Flexible sigmoidoscopy
    • Advantage: does not require extensive bowel preparation before the procedure.
    • Disadvantage: The rest of the colon is not visualized.
  • Colonoscopy (confirmatory test)
    • Preferred screening tool for diagnosed cases of hereditary polyposes/colonic cancer
    • Advantages: Enables biopsy, histological confirmation, and therapeutic polypectomy (see “Classification” above)
    • Disadvantages: Requires bowel preparation with laxatives; Risk of bowel perforation.

References:[1]

Treatment

Treatment depends on the etiology and nature of the polyp or polyps.

References:[1][2]