Colon (tumor & nontumor)
Inflammatory polyp

Topic Completed: 1 November 2017

Minor changes: 31 July 2020

Copyright: 2002-2019,, Inc.

PubMed Search: "Inflammatory polyp" colon

Andrew L.J. Dunn, M.D.
Raul S. Gonzalez, M.D.
Page views in 2019: 29,759
Page views in 2020 to date: 16,024
Cite this page: Dunn A, Gonzalez R. Inflammatory polyp. website. Accessed August 14th, 2020.
Definition / general
Essential features
  • Nonneoplastic colon polyp composed of inflamed mucosa
  • Typically shows surface erosion with surrounding granulation tissue and epithelial distortion
ICD coding
  • K51.4 inflammatory polyps of colon
  • Typically second and third decades for inflammatory bowel disease; incidence range of 10 - 20% in ulcerative colitis patients (World J Gastroenterol 2017;23:1541)
  • May occur in older patients with peripheral vascular disease
  • Can arise anywhere in the colon, especially at the ileocecal region in Crohn’s disease
  • May form at anastomotic sites
  • Believed to be secondary to repeated bouts of intense inflammation
  • Formation of inflammatory polyps may be related to increases in C-reactive protein, C4 and procollagen III peptide (World J Gastroenterol 2003;9:619)
Clinical features
  • Sporadic inflammatory polyps are usually incidental at colonoscopy
  • May present with intussusception or obstructive symptoms
  • Presence of pseudopolyps in inflammatory bowel disease may represent recent flare, although lesions are found in active or dormant disease (World J Gastroenterol 2017;23:1541); also may be related to arthropathy or other extracolonic symptoms (Lancet 1969;2:555)
Case reports
  • Typically treated endoscopically via polypectomy
  • Examples related to inflammatory bowel disease may improve with infliximab (J Crohns Colitis 2010;4:707)
  • Argon plasma coagulation or ablation for bleeding control
  • Surgical resection if profuse bleeding, obstruction or intussusception
Clinical images

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Endoscopy of inflammatory polyp in the sigmoid colon

Gross description
  • Usually sessile and less than 3 cm
  • May be pedunculated or filiform
Gross images

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Inflammatory pseudopolyps in ulcerative colitis

Microscopic (histologic) description
  • Often consists of normal colonic mucosa in a polypoid configuration, with increased inflammation (expanded lamina propria and crypt abscesses or cryptitis)
  • Epithelium can show various degrees of surface erosion, crypt distortion / dilation or hyperplasia, along with reactive nuclear features within the mucosal epithelial cells
  • May consist entirely of granulation tissue (abundant thin walled and dilated vessels surrounded by mixed neutrophilic and lymphoplasmacytic inflammation)
  • Reactive stromal cells may be markedly pleomorphic and mimic sarcoma
  • Cases associated with inflammatory bowel disease may rarely show epithelial dysplasia
Microscopic (histologic) images

Contributed by Andrew L.J. Dunn, M.D.

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Ulcerative colitis

Annotated images

Negative stains
Molecular / cytogenetics description
  • Usually no abnormalities

Inflammatory polyp on colonoscopy

Differential diagnosis
Board review style question #1
Which of the following is NOT a typical feature of inflammatory polyps?

  1. Crypt distortion / branching
  2. Granulation tissue changes
  3. Microsatellite instability
  4. Surface mucosal erosion
Board review answer #1
C. Microsatellite instability; inflammatory polyps are a benign process with various degrees of mucosal erosion, increased vascular density similar to granulation tissue and architectural changes.

Reference: Colon tumor - Inflammatory polyp of colon

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