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
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
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
Comment Here
Reference: Inflammatory fibroid polyp
Comment Here
Reference: Inflammatory fibroid polyp