Case 1 -
Inflammatory Fibroid Polyp
Johns Hopkins Hospital
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Transverse colon mass in a 66 year old man. Initially,
a small biopsy was received on which several observers were unable to make a diagnosis. In the interim,
the patient became obstructed and a resection was performed.
Case 1 - Slide 1
Case 1 - Figure 1 - Low magnification of this colon lesion. The epicenter of the process is in the submucosa but the overlying mucosa has been affected and displays marked reactive epithelial changes and crypt distortion.
Case 1 - Figure 2 - Higher magnification of the surface mucosa. On mucosal biopsies, this process was virtually impossible to diagnose.
Case 1 - Figure 3 - The submucosal lesion is characterized by spindle cells arranged in whorls around vessels.
Inflammatory Fibroid Polyp.
The first systematic description of these tumors was provided
by J Vaněk and appeared in the American Journal of Pathology in 1949  although there were prior
case reports. Helwig and Ranier coined the present term in the early 1950s  but these lesions have
been called "gastric submucosal granuloma with eosinophilic infiltration, eosinophilic granuloma,
granuloblastoma, neurofibroma, and hemangiopericytoma. The vast majority occur in the stomach where they
account for about 3-4% of all gastric polyps
but they have been reported throughout the
In Stolte's large comprehensive series, patients with gastric
examples were typically 60- 80 years old, but examples are recorded in young adults and the elderly.
Most are found in the gastric antrum, but other gastric sites are known. Their endoscopic appearance is
that of a smooth submucosal lesion that can be pedunculated or sessile with surface ulceration/erosion in
about a third of cases. Presentation is somewhat site specific, in that small intestinal examples can
lead to intussusception or obstruction and gastric examples are found in patients with pain and nausea
and vomiting. Inflammatory fibroid polyps are probably reactive in nature, but an interesting family
with these lesions in females for three generations has been reported (
cytometry in one case showed diploidy . A literature search disclosed no reports of cytogenetic
anomalies in these polyps. These are benign lesions and seldom recur after excision. Japanese examples
have been found in association with gastric dysplasia/carcinoma (presumably based on coincidence)
not Western ones.
Histologically, these tumors are well-marginated but non-encapsulated and affect the mucosa and
submucosa. They are composed of uniform spindled cells, mixed inflammatory cells, and prominent
vasculature. The spindle cells have amphophilic elongate cytoplasm and pale ovoid to spindle shaped
nuclei with variable collagen deposition. Most examples display a whorled "onion-skin" proliferation
around vessels and all examples are punctuated by abundant background eosinophils, lymphocytes, and
plasma cells. Mitoses are infrequent.
The immunohistochemical and ultrastructural profile of the proliferating cells is that of
modified fibroblasts/myofibroblasts, with variable actin but no S100 protein or epithelial markers
. Some authors believe that their consistent expression of cyclin D1 and fascin suggests that they
are of dendritic cell origin  but their key feature is consistent CD34 reactivity in small tumors and
less consist staining in larger lesions . This latter finding, of course, raises the differential
diagnostic consideration of gastrointestinal stromal tumors, but the morphology is different and
inflammatory fibroid polyps lack CD117. In large examples, sarcomas are often considered but the bland
appearance of the proliferating cells and the inflammatory background argue against this interpretation.
Note the striking epithelial changes on the eroded surface, which makes one consider an epithelial lesion
on mucosal biopsies!
Immunohistochemistry, Inflammatory Fibroid polyp:
- Gastrointestinal Stromal Tumors (GIST) - This is an important distinction as the management and prognosis are very different. The loose edematous stroma rich in inflammatory cells especially eosinophils; concentrically arranged stromal cells around blood vessels as well as negative CD117 immunostain are all helpful in differentiating IFP from GIST. Inflammatory fibroid polyps can contain occasional mitoses but no atypical mitoses.
- Eosinophilic gastroenteritis- Does not present as a single mass. Histologic findings include patchy eosinophilic infiltrate of mucosa, submucosa, muscularis propria or serosa. History of peripheral eosinophila, asthma and younger age at presentation are also distinguishing clinical features.
- Benign mesenchymal tumors such as schwannoma, leiomyoma, solitary fibrous tumor can be distinguished by lack of eosinophils, typical morphology, positive immunostains for S-100 (schwannoma), desmin (leiomyoma), and bcl-2 (solitary fibrous tumor) respectively.
- Parasitic infection-Such as schistosomiasis, anisakiasis or strongyloides can cause intense granulomatous reaction with eosinophils and may be mistaken for an IFP. Findings such as schistosome egg or strongyloides larvae will rule out an IFP.
- Vanek J. Gastric submucosal granuloma with eosinophilic infiltration. Am J Pathol. 1949;25:397-411.
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- Stolte M, Sticht T, Eidt S, Ebert D, Finkenzeller G. Frequency, location, and age and sex distribution of various types of gastric polyp. Endoscopy. 1994;26(8):659-65.
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- Allibone RO, Nanson JK, Anthony PP. Multiple and recurrent inflammatory fibroid polyps in a Devon family ('Devon polyposis syndrome'): an update. Gut. 1992;33(7):1004-5.
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