Gastrointestinal Pathology

Inflammatory Fibroid Polyp

Elizabeth Montgomery
Johns Hopkins Hospital
Baltimore, MD


Clinical History
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.


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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.
Figure 2 - Higher magnification of the surface mucosa. On mucosal biopsies, this process was virtually impossible to diagnose.
Figure 3 - The submucosal lesion is characterized by spindle cells arranged in whorls around vessels.

Figure 4 - Note the numerous eosinophils in the background.
Figure 5 - The cytologic features of the proliferating spindle cells are bland.


Diagnosis
Inflammatory Fibroid Polyp.

Discussion
The first systematic description of these tumors was provided by J Vaněk and appeared in the American Journal of Pathology in 1949 [1] although there were prior case reports. Helwig and Ranier coined the present term in the early 1950s [2] 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 [3, 4, 5, 6, 7, 8, 9], but they have been reported throughout the gastrointestinal tract [3, 6, 7, 10, 11, 12, 13, 14, 15, 16]. 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 ( "Devon polyposis" [17, 18] ). Flow cytometry in one case showed diploidy [19]. 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) [20]but 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 [10, 12] . Some authors believe that their consistent expression of cyclin D1 and fascin suggests that they are of dendritic cell origin [10] but their key feature is consistent CD34 reactivity in small tumors and less consist staining in larger lesions [20]. 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:

Differential Diagnosis:
  • 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.

References
  1. Vanek J. Gastric submucosal granuloma with eosinophilic infiltration. Am J Pathol. 1949;25:397-411.

  2. Helwig E, Ranier A. Inflammatory fibroid polyps of the stomach. Surg Gynecol Obstets. 1953;96:355-367.

  3. Ali J, Qi W, Hanna SS, Huang SN. Clinical presentations of gastrointestinal inflammatory fibroid polyps. Can J Surg. 1992;35(2):194-8.

  4. Allman RM, Cavanagh RC, Helwig EB, Lichtenstein JE. Radiologic-pathologic correlation from the Armed Forces Institute of Pathology. Inflammatory fibroid polyp. Radiology. 1978;127(1):69-73.

  5. Harned RK, Buck JL, Shekitka KM. Inflammatory fibroid polyps of the gastrointestinal tract: radiologic evaluation. Radiology. 1992;182(3):863-6.

  6. Johnstone JM, Morson BC. Inflammatory fibroid polyp of the gastrointestinal tract. Histopathology. 1978;2(5):349-61.

  7. Santos Gda C, Zucoloto S. Inflammatory fibroid polyp. Review of the literature. Arq Gastroenterol. 1993;30(4):107-11.

  8. Stolte M, Finkenzeller G. Inflammatory fibroid polyp of the stomach. Endoscopy. 1990;22(5):203-7.

  9. 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.

  10. Pantanowitz L, Antonioli DA, Pinkus GS, Shahsafaei A, Odze RD. Inflammatory fibroid polyps of the gastrointestinal tract: evidence for a dendritic cell origin. Am J Surg Pathol. 2004;28(1):107-14.

  11. Nkanza NK, King M, Hutt MS. Intussusception due to inflammatory fibroid polyps of the ileum: a report of 12 cases from Africa. Br J Surg. 1980;67(4):271-4.

  12. Suster S, Robinson MJ. Inflammatory fibroid polyp of the small intestine: ultrastructural and immunohistochemical observations. Ultrastruct Pathol. 1990;14(2):109-19.

  13. Trillo AA, Rowden G. The histogenesis of inflammatory fibroid polyps of the gastrointestinal tract. Histopathology. 1991;19(5):431-6.

  14. Widgren S, Pizzolato GP. Inflammatory fibroid polyp of the gastrointestinal tract: possible origin in myofibroblasts? A study of twelve cases. Ann Pathol. 1987;7(3):184-92.

  15. Widgren S, Cox JN. Inflammatory fibroid polyp in a continent ileo-anal pouch after colectomy for ulcerative colitis--case report. Pathol Res Pract. 1997;193(9):643-7; discussion 649-52.

  16. Campbell AP, Mortensen N. Inflammatory fibroid polyps in Crohn's disease. Histopathology. 1993;22(4):405.

  17. 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.

  18. Anthony PP, Morris DS, Vowles KD. Multiple and recurrent inflammatory fibroid polyps in three generations of a Devon family: a new syndrome. Gut. 1984;25(8):854-62.

  19. Villanacci V, Grigolato PG, Cadei M, Cestari R, Ravelli P, Missale G. [Flow cytometry sutdy of DNA and cell kinetics in the adenoma- carcinoma sequence in the large intestine]. Pathologica. 1998;90(2):120-6.

  20. Hasegawa T, Yang P, Kagawa N, Hirose T, Sano T. CD34 expression by inflammatory fibroid polyps of the stomach. Mod Pathol. 1997;10(5):451-6.