Colon tumor
Polyps
Inflammatory fibroid polyp

Editor-in-Chief: Debra Zynger, M.D.
Taofic Mounajjed, M.D.

Topic Completed: 5 March 2019

Revised: 14 June 2019

Copyright: 2003-2019, PathologyOutlines.com, Inc.

PubMed Search: Inflammatory fibroid polyp AND colon


Taofic Mounajjed, M.D.
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Cite this page: Mounajjed T. Inflammatory fibroid polyp. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/colontumorinflammatoryfibroid.html. Accessed December 11th, 2019.
Definition / general
  • Uncommon benign nonepithelial submucosa based polyp that can arise throughout the gastrointestinal tract
Essential features
  • Benign submucosa based polyp that frequently ulcerates
  • Consists of bland spindle cells, inflammatory cells with prominent eosinophils and a rich vascular network
  • Immunohistochemical positivity for CD34 and PDGFR
  • Frequently harbors activating mutations involving PDGFRA gene
Terminology
  • Previously known as Vanek tumors
  • Inflammatory fibroid polyp is preferred
Epidemiology
Sites
  • Can arise throughout the gastrointestinal tract
  • Most common sites are the gastric antrum and the terminal ileum
  • ~12 - 37% of lesions arise in the colon (Am J Surg Pathol 2013;37:586, Radiology 1992;182:863)
  • Majority of colonic lesions are found in the rectosigmoid
Pathophysiology
Clinical features
Diagnosis
  • Made by histologic examination
Case reports
Treatment
Gross description
  • Sessile polyps centered in the colonic submucosa
  • Usually solitary
  • Often ulcerated
  • 1.5 - 7 cm (mean 3 - 4 cm) (Dig Dis Sci 1999;44:1810)
Gross images

Contributed by Taofic Mounajjed, M.D.

Ileocecal valve polyp with intussusception

Pedunculated cecal polyp

Cut surface with white color

Microscopic (histologic) description
  • Usually centered in the submucosa but often extends into the overlying mucosa with associated ulceration
  • Consists of a loose mixture of the following elements, embedded in an edematous / myxoid background:
    • Bland spindle shaped mesenchymal cells
    • Inflammatory cells, including prominent eosinophils; lymphocytic aggregates may be present
    • Vascular network consisting of variably sized blood vessels
  • Mesenchymal spindle cells can aggregate in a concentric fashion around the blood vessels and mucosal crypts; eosinophils may also concentrate around blood vessels
  • Colonic lesions can infiltrate the muscularis propria or even the serosa, unlike gastric inflammatory fibroid polyps
  • Extension into the mucosa can cause mucosal atrophy and distortion
  • Mitotic figures are infrequent; atypical mitoses are absent
  • Fascicular growth with lack of prominent eosinophils is seen in a minority of cases
  • Stroma can sometimes show hyalinization (Am J Surg Pathol 2013;37:586)
Microscopic (histologic) images

Contributed by Taofic Mounajjed, M.D.

Submucosal polyp

Ulcerated mucosa

Entrapped muscularis mucosa

Bland spindle cells


Rich vascular network

Mesenchymal cells

CD34


Virtual slides

Images hosted on other servers:

Inflammatory fibroid polyp

Negative stains
Electron microscopy description
  • Spindle cells have features suggestive of a primitive submucosal stromal cell phenotype with incomplete fibrohistiocytic differentiation (Ultrastruct Pathol 1990;14:109)
    • Abundant rough endoplasmic reticulum and active production of collagen in many of the cells
    • Dendritic cytoplasmic projections with large cytoplasmic vacuoles containing phagocytosed cellular debris in others
    • Some cells contain oligocilia and primitive intercellular junctions
Molecular / cytogenetics description
Differential diagnosis
  • Gastrointestinal stromal tumor:
    • Centered in the muscularis propria rather than the submucosa
    • More cellular, spindled cells are more plump, can contain skeinoid fibers, inflammation and eosinophils not usually prominent
    • KIT+, DOG1+
    • Both express CD34 and can harbor PDGFRA mutations
  • Inflammatory myofibroblastic tumor:
    • More common in children
    • Larger size, less prominent vasculature, plasma cells rather than eosinophils are usually prominent
    • CD34-, ALK+, smooth muscle actin+, desmin+
    • Translocation with fusion gene (TPM3-ALK) present in 50% of cases; lacks PDGFRA mutation
  • Schwannoma:
    • Deeper location in the wall
    • Antoni A and Antoni B, Verocay bodies, hyalinized vessels, peripheral cuff of lymphoid aggregates, eosinophils not prominent
    • S100+, SOX10+, CD34-
  • Inflammatory pseudopolyp:
    • Usually develops as a response to a diffuse (example: inflammatory bowel disease) or localized inflammatory process
    • Often multiple
    • CD34-
    • Lacks PDGFRA mutation
Board review question #1
A sessile polyp was resected from the ascending colon of a 48 year old woman

Which of the following statements regarding this polyp is correct?

  1. Colon is the most common location for this polyp
  2. Eosinophils are only seen in 10% of cases
  3. Lesions are centered in the muscularis propria
  4. Lesion stains positively with CD34
  5. Lesion stains positively for DOG1
Board review answer #1
D. Lesion stains positively with CD34

Reference: Colon tumor - Inflammatory fibroid polyp

Comment here
Board review question #2
Which of the following statements regarding colonic inflammatory fibroid polyps is correct?

  1. ~20% undergo malignant transformation
  2. Frequently harbor activating mutations of PDGFRA
  3. Most commonly arise in association with inflammatory bowel disease
  4. Most commonly develop in children
  5. Often positive for KIT
Board review answer #2
B. Frequently harbor activating mutations of PDGFRA

Reference: Colon tumor - Inflammatory fibroid polyp

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