Inflammatory fibroid polyp

Colon (tumor & nontumor)

Polyps

Author: Taofic Mounajjed, M.D.

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

Topic Completed: 5 March 2019

Minor changes: 31 July 2020

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

PubMed Search: Inflammatory fibroid polyp AND colon

Page views in 2019: 6,127

Page views in 2020 to date: 3,848

Table of Contents

Cite this page: Mounajjed T. Inflammatory fibroid polyp. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorinflammatoryfibroid.html. Accessed August 6th, 2020.

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
- CD34 (82 - 100%)
- PDGFR, vimentin, fascin , cyclin D1 and calponin (88%) (Am J Surg Pathol 2004;28:107, Am J Surg Pathol 1993;17:1159, Mod Pathol 1997;10:451, Virchows Arch 2010;456:491, Appl Immunohistochem Mol Morphol 2000;8:147, Mod Pathol 2000;13:1134)

Negative stains

KIT, DOG1, S100
SMA (25% positive)
CD35 (can be focally positive)

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:
- 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 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 answer #1

D. Lesion stains positively with CD34

Reference: Colon tumor - Inflammatory fibroid polyp

Comment here

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 answer #2

B. Frequently harbor activating mutations of PDGFRA

Reference: Colon tumor - Inflammatory fibroid polyp

Comment here