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Quick Facts
- The incidence of polyps increases with age
- Most patients with polyps are asymptomatic
- Colonic polyps can be classified as hyperplastic polyps, adenomas, and polyposis syndromes
- The malignant potential of adenomas correlates with size and histologic features
Colonic Polyps: Pathology

Background

A polyp is a protuberance of tissue that can grow into the lumen of the colonic mucosa and may be shaped like the stalk of a mushroom.1 It takes approximately 5 to 10 years for a polyp 10 mm in size to develop malignant transformation.1 Colonoscopic removal of polyps and subsequent surveillance can reduce the incidence of colon cancer by 90%.1,2 Although polyps are usually asymptomatic, they may cause ulceration, bleeding, abdominal pain, and intestinal obstruction.

Colonic polyps can be further classified as hyperplastic polyps, adenomas, and polyposis syndromes. Rule

Hyperplastic Polyps1,3

  • Most common, > 5 mm in size
  • Accounts for up to 20% of all surgically removed polyps
  • Typically located in the distal sigmoid colon and rectum; they rarely develop into colorectal cancer
  • Most commonly diagnosed in individuals aged 50- to 70 years old

Rule

Adenomas

  • Comprise 10% of all colonic polyps
  • Malignant potential of adenomas correlates with size and dysplastic features3
  • Greater than 90% of all colonic polyps are > 1.5 cm in size
    • Three types of adenomas:
      • Tubular: most common, may be penduculated or sessile1,3, found anywhere in the colon
      • Tubularvillous (TV): most commonly found in the right colon, intermediate in size, varying between 1 to 10 cm.1
      • Villous adenomas: occur more frequently in the rectum, larger that tubular or tubularvillous adenomas, “cauliflower-like appearance,”1 may cause rectal bleeding or mucous discharge, have areas of malignant change3

Adenomatous colon polyps, probability of malignancy by size and type4

 

Size (cm)

 

< 1

1–2

> 2

Tubular

1%

10%

34%

Mixed (TV)

4%

9%

45%

Villous

10%

10%

54%

  • Most colon polyps (90%) are hyperplastic (size < 5 mm)
  • 93% of CRC arise from adenomatous polyps

From Kahn,4 with permission.

Rule

Polyposis Syndrome:

  • Two types of hereditary syndromes and other subtypes may predispose individuals to colorectal cancer:
    • Familial adenomatous polyposis (FAP): 100% likelihood of developing cancer by age 55; screening should begin in the teenage years; adenomatous polyps may coat the entire length of large bowel.1-3
    • Hereditary nonpolyposis colorectal cancer (HNPCC): autosomal-dominant includes Lynch I (cancer in large bowel) and Lynch II (cancer located in a variety of tumor sites),2,3 Individuals develop cancer at an early age, and screening should begin by age 20 for relatives of patients who have this diagnosis.

Please refer to the Gastrolab endoscopy image library, available at: http://www.gastrolab.net/ksgcoad1.htm,5 for endoscopic pictures of various adenomas. Accessed December 14, 2010.

Rule

References

  1. Pearlman J. Colon, polyps. Available at: http://emedicine.com/RADIO/topic185.htm Accessed  December 14, 2010.
  2. Goldberg R. Gastrointestinal cancers. In: Casciato DA, Lowitz BB, eds. Manual of Clinical Oncology. Philadelphia: Lippincott Williams & Wilkins 2000:172-217.
  3. Stemmermann G, Fenoglio-Prieser C. Pathology and natural history of colorectal cancer. In: Abbruzzese JL, Evans DB, Willett CG, Fenoglio-Preiser C, eds. Gastrointestinal Oncology. New York: Oxford University Press; 2003:665-675.
  4. Kahn CE. Adenomatous colon polyps. Available at: http://chorus.rad.mcw.edu/doc/00438.html  Accessed December 14, 2010.
  5. The Gastrolab Endoscopic Image Library. Polyps in the colon.  Available at: http://www.gastrolab.net/ksgcoad1.htm. Accessed december 14, 2010.

Rule

 



Article Created On : 4/23/2009 11:07:00 AM             Article Updated On : 12/14/2010 3:58:15 PM