Colon
Polyps
Inflammatory fibroid polyp
Author: Taofic Mounajjed, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Last author update: 5 March 2019
Last staff update: 16 June 2022
Copyright: 2003-2022, PathologyOutlines.com, Inc.
PubMed Search: Inflammatory fibroid polyp AND colon
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Sites | Pathophysiology | Clinical features | Diagnosis | Case reports | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Virtual slides | Positive stains | Negative stains | Electron microscopy description | Molecular / cytogenetics description | Differential diagnosis | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2Cite this page: Mounajjed T. Inflammatory fibroid polyp. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorinflammatoryfibroid.html. Accessed July 5th, 2022.
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
- Patients of all ages can be affected; average age 46 - 60 years (Am J Surg Pathol 2013;37:586)
- Slight female predominance (Radiology 1992;182:863)
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
- Majority (~70%) have PDGFRA mutations (J Pathol 2000;216:176, Histopathology 2012;61:59)
- Mutated submucosal mesenchymal progenitor cells of undetermined type likely develop into a tumor
Clinical features
- No established clinical associations
- Reported in patients with inflammatory bowel disease, Cowden syndrome and von Recklinghausen disease (Pathol Res Pract 1997;193:643, AJR Am J Roentgenol 1995;165:1012, Histopathology 1992;20:545, Endoscopy 2018 Jan;50:E5)
- Patients often have nonspecific symptoms of diarrhea, abdominal pain / discomfort, weight loss (Dig Dis Sci 1999;44:1810)
- Can rarely be complicated by intussusception or intestinal obstruction (Rev Hosp Clin Fac Med Sao Paulo 1997;52:20)
Diagnosis
- Made by histologic examination
Case reports
- 39 year old woman with past history of type 1 neurofibromatosis (Endoscopy 2018 Jan;50:E5)
- 59 year old Nigerian with rectal polypoidal mass (Afr Health Sci 2016;16:873)
- 65 year old woman with mild paroxysmal pain (Chin Med J (Engl) 2017;130:2130)
- 72 year old woman who underwent a right hemicolectomy (Ann Clin Lab Sci 2015;45:441)
- Case with PDGFRA expression (Pathol Int 2018;68:205)
Treatment
- Local excision is curative (Dig Dis Sci 1999;44:1810)
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
Positive stains
- Spindle cells
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
- Activating mutations of the platelet derived growth factor receptor α gene (PDGFRA) in most, detected by PCR or sequencing
- PDGFRA mutations might be less frequent in colon in comparison to the stomach and small intestine (Histopathology 2012;61:59, Mod Pathol 2009;22:1049, J Pathol 2000;216:176)
Differential diagnosis
- Gastrointestinal stromal tumor:
- 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:
- 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 style 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?
- Colon is the most common location for this polyp
- Eosinophils are only seen in 10% of cases
- Lesions are centered in the muscularis propria
- Lesion stains positively with CD34
- Lesion stains positively for DOG1
Board review style answer #1
Board review style question #2
Which of the following statements regarding colonic inflammatory fibroid polyps is correct?
- ~20% undergo malignant transformation
- Frequently harbor activating mutations of PDGFRA
- Most commonly arise in association with inflammatory bowel disease
- Most commonly develop in children
- Often positive for KIT
Board review style answer #2
B. Frequently harbor activating mutations of PDGFRA
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Reference: Inflammatory fibroid polyp
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Reference: Inflammatory fibroid polyp
