Colon polyps pathophysiology: Difference between revisions

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**    Sessile serrated polyps
**    Sessile serrated polyps
** Traditional serrated adenomas
** Traditional serrated adenomas
*** They are protuberant and pedunculated polyps, less than 1.5 cm, which are located in left colon.  
*** They are protuberant and pedunculated [[Polyp|polyps]], less than 1.5 cm, which are located in left [[Colon (anatomy)|colon]].  
* Serration
*** They have [[Cell biology|cytological]] [[dysplasia]] including [[Cell nucleus|nuclear]] transformation, irregular [[Cell nucleus|nuclear]] polarity, and serration.
*     BRAF mutation
*** [[Cell biology|Cytological]] [[dysplasia]] causes crypts that are irregular and branching. 
*     KRAS mutation
*** 
 
==== Adenomatous polyps ====
==== Adenomatous polyps ====
*
*

Revision as of 20:09, 23 January 2018

Colon polyps Microchapters

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sadaf Sharfaei M.D.[2]

Overview

Any form of unregulated growth in the colon may cause polyps. The exact etiology is unclear. However, risk factors may contribute to the formation of polyps. There are four different types of polyps including inflammatory, hamartomatous, serrated, and adenomatous polyps, which have different pathogenesis. Inflammatory polyps are non-neoplastic polyps that occur following intestinal inflammation, infections, or ischemia. Hamartomatous polyp is an overgrowth of mature cells and connective tissue elements including smooth muscle, lamina propria, and cartilage, and fat. They are covered by a hypertrophic epithelium. Serrated polyps are different polyps which have variable malignant potential. They include hyperplastic, sessile serrated and traditional serrated polyps. Hyperplastic polyps are the most common polyps. Hyperplastic polyp is infolding of the crypt epithelium that forms serration or saw-toothed appearance.

Pathophysiology

Pathogenesis

  • Any form of unregulated growth in the colon may cause polyps. The exact etiology is unclear. However, risk factors may contribute to the formation of polyps.
  • There are four different types of polyps including inflammatory, hamartomatous, serrated, and adenomatous polyps, which have different pathogenesis.
  • The pathophysiology of colon polyps depends on the histological type.

{{#ev:youtube|oJU7CokNLZY}} {{#ev:youtube|7n5EnaLOV54}}

Inflammatory polyps

Hamartomatous polyps

Serrated polyps

  • Serrated polyps are different polyps which have variable malignant potential. They include hyperplastic, sessile serrated and traditional serrated polyps. They have various histopathologies and manifestations.
    • Hyperplastic polyps are the most common polyps.
      • They are small outpouching, less than 5 mm, which are located mostly in rectosigmoid area.
      • Hyperplastic polyp is infolding of the crypt epithelium that forms serration or saw-toothed appearance.
      • The molecular basis of this transformation is still unclear. However, it has been attributed to failure of apoptosis.
      • BRAF mutations are associated with crypt serration.
      • There are three different subtypes of hyperplastic polyps based on degree of serration and content, including microvesicular type, goblet cell–rich type, and mucin-poor type.
    • Sessile serrated polyps
    • Traditional serrated adenomas

Adenomatous polyps

Genetics

  • The development of colon polyps is the result of multiple genetic mutations.
  • Genetic mutations might cause hereditary polyps disorders.

Familial adenomatous polyposis (FAP)

  • FAP is due to mutations in the following genes:
    • APC gene, which is located on chromosome 5 in band q21 or band q22 (5q21-q22)
    • MUTYH gene, which is located on chromosome 1 between bands p34.2 and p32.1 (5p34.3-p32.1)
    • MYH-associated polyposis (MAP) is caused by mutations in the MYH gene.

Peutz-Jeghers syndrome

Gardner's syndrome

Serrated polyposis syndrome

  • They develop multiple serrated adenomatous polyps in the upper part of the colon.

Familial juvenile polyposis

  • It is an autosomal dominant disorder. 
  • It increases risk of colorectal cancer
  • It has extra-colonic tumors. 
  • There has been some association with the following genes:

Gross Pathology

  • On gross pathology, outpouching, pedunculated or flat lesions are characteristic findings of colon polyps.
Villous adenoma of the transverse colon By http://web2.airmail.net/uthman/specimens/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=840194
Tubulovillous Polyp of the Colon By http://web2.airmail.net/uthman/specimens/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=840172
Tubulovillous Polyp of the Colon By http://web2.airmail.net/uthman/specimens/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=840176
Adenomatous Polyp of the Colon By http://web2.airmail.net/uthman/specimens/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=840154
Adenomatous Polyp of the Colon By http://web2.airmail.net/uthman/specimens/index.html, Public Domain, https://commons.wikimedia.org/w/index.php?curid=840157
Longitudinally opened freshly resected colon segment showing a cancer and four polyps. Plus a schematic diagram indicating a likely field defect (a region of tissue that precedes and predisposes to the development of cancer) in this colon segment. The diagram indicates sub-clones and sub-sub-clones that were precursors to the tumors. Source: Wikimedia.org By Bernstein0275 - Own work, CC BY-SA 3.0[4]
Colon polyp on colonoscopy By 邱鈺鋒 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=37027826

Microscopic Pathology

Hyperplastic polyp of the Colon. By Patho - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=19409502
Micrograph of a colorectal hyperplastic polyp. H&E stain. By Nephron - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=6427545
Colon adenoma By No machine-readable author provided. KGH assumed (based on copyright claims). - No machine-readable source provided. Own work assumed (based on copyright claims)., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=444694


References

  1. Shussman, N.; Wexner, S. D. (2014). "Colorectal polyps and polyposis syndromes". Gastroenterology Report. 2 (1): 1–15. doi:10.1093/gastro/got041. ISSN 2052-0034.
  2. Li SC, Burgart L (2007). "Histopathology of serrated adenoma, its variants, and differentiation from conventional adenomatous and hyperplastic polyps". Arch. Pathol. Lab. Med. 131 (3): 440–5. doi:10.1043/1543-2165(2007)131[440:HOSAIV]2.0.CO;2. PMID 17516746.
  3. Zbuk KM, Eng C (2007). "Hamartomatous polyposis syndromes". Nat Clin Pract Gastroenterol Hepatol. 4 (9): 492–502. doi:10.1038/ncpgasthep0902. PMID 17768394.
  4. "File:Image of resected colon segment with cancer & 4 nearby polyps plus schematic of field defects with sub-clones.jpg - Wikimedia Commons".

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