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Inflammatory Fibroid Polyp

Definition

  • Gastrointestinal tract tumor characterized by spindle and stellate cells set in an inflammatory, myxoid stroma

Alternate/Historical Terms

  • Vanek tumor

Diagnostic Criteria

  • Most are semi-pedunculated polyps arising in the submucosa
    • Covered by mucosa or may be eroded
    • Occasional tumors may be restricted to the lamina propria and muscularis mucosae
    • Larger tumors may extend into muscularis propria
    • Most <5 cm, rarely up to 20 cm
  • Composed of bland, uniform spindled and/or stellate cells
    • The lesional cells may be lost in the background and difficult to identify
    • Multinucleated giant cells in 1/3 of cases
  • Loose fibromyxoid background with regular vascular pattern
    • Regular small to medium sized vessels throughout
    • May have granulation tissue appearance
  • Eosinophil rich mixed inflammatory infiltrate
    • Also includes lymphocytes, plasma cells, macrophages, mast cells
    • Lymphoid aggregates may be seen
      • Germinal centers unusual
  • Frequent whorled, concentric “onion skin” pattern centered on blood vessels and glands
    • 10% of cases may lack this pattern
      • May be accentuated by CD34 stain
      • It has been proposed that lack of this pattern correlates with large size but this is not supported by several studies
  • Most common in gastric antrum, followed by small intestine
      • Less common in esophagus and colorectum

    Robert V Rouse MD
    Department of Pathology
    Stanford University School of Medicine
    Stanford CA 94305-5342

    Original posting/updates: 12/5/09, 11/27/11

Supplemental studies

Immunohistology

    CD34 80-90%
    Fascin 100%
    CD35 100% (10% of cells)
    Cyclin D1 100%
    Calponin 88%
    Smooth muscle actin 25%
    CD117 (CKIT) 0%
    DOG1 0%
    S100 0%
    EMA, Keratin, Desmin, bcl2 0%
    • It has been proposed that IFPs that do not demonstrate a whorled concentric pattern make up the CD34 negative pattern (Kim 2000)
      • This would suggest that IFP is made up of more than one process
    • Expression of fascin and CD35 has been presented as evidence of dendritic cell origin (Pantanowitz 2004)

    Genetic Studies

    • Activating mutations in PDGFRA identified in 70% of cases
      • Mutations identical to those seen in GIST
      • Suggests that IFP are neoplastic

    Differential Diagnosis

    Inflammatory Fibroid Polyp GIST (spindled, bland)
    Submucosal Intramural
    Spindled and stellate cells Spindled but no stellate cells
    Abundant stromal eosinophils Eosinophils infrequent
    Perivascular concentric cuffing common Lacks concentric cuffing
    Fibromyxoid background with regular vascular pattern May be myxoid but lacks regular vascular pattern
    CD117 negative CD117 74-95%
    DOG1negative DOG1 87-94%
    Both are frequently CD34 positive

    Inflammatory Fibroid Polyp

    Solitary Fibrous Tumor

    Submucosal

    In GI tract, arises in serosa

    Regular small to medium size vascular pattern

    HPC-like vessels common

    Fibromyxoid stroma

    Ropy collagen

    Eosinophil rich inflammatory stroma

    Inflammation infrequent
    Both are usually CD34 positive and may have a perivascular whirling pattern

    Inflammatory Fibroid Polyp GI Schwannoma
    Eosinophil rich inflammatory infiltrate throughout Peripheral lymphoid cuff common
    Perivascular concentric cuffing common, palisading rare May palisade, no concentric pattern
    Fibromyxoid background with regular vascular pattern May be myxoid but lacks regular vascular pattern
    S100 negative S100 100%

    Inflammatory Myofibroblastic Tumor Inflammatory Fibroid Polyp
    Usually in children Rare in children
    Frequently associated with systemic signs and symptoms Not associated with systemic signs and symptoms
    Plasma cells > eosinophils Eosinophils > plasma cells
    Frequently positive for desmin, keratin and ALK Desmin, keratin and ALK negative
    Nuclear pleomorphism frequent Cytologically bland
    Lacks regular vascular pattern Regular vascular pattern
    May have necrosis and calcification Necrosis and calcification rare
    CD34 negative CD34 80-90%

    Inflammatory Fibroid Polyp GI Perineurioma
    Submucosal Predominantly lamina propria
    Eosinophil rich inflammatory infiltrate Eosinophils and inflammation infrequent
    Perivascular concentric cuffing common Lacks prominent concentric cuffing
    Fibromyxoid background with regular vascular pattern Rarely may be myxoid but lacks regular vascular pattern
    CD34 positive in 80% CD34 weak focal in 15-30%

    Inflammatory Fibroid Polyp Leiomyoma
    Desmin negative Desmin positive
    Spindled and stellate cells Spindled but no stellate cells
    Abundant stromal eosinophils Eosinophils infrequent
    Perivascular concentric cuffing common Lacks concentric cuffing
    Fibrous or myxoid background May be myxoid but usually no fibrous background

    Inflammatory Fibroid Polyp Gastric Plexiform Fibromyxoma
    Usually solitary nodule Multinodular, plexiform
    Usually a pedunculated polyp Intramural
    Centered on submucosa Centered on muscularis propria
    Frequent inflammatory infiltrate No intrinsic inflammatory infiltrate
    May have concentric perivascular pattern of spindle cells Lacks concentric pattern
    CD34 frequently positive CD34 negative

    Clinical

    • Mean age about 60
      • Range 39-85
    • May present with intussusception, obstruction, bleeding
    • Infrequently recurs
    • No metastases or local aggressive recurrences
    • One known kindred of familial IFP
      • 5 females in 3 generations
      • Termed Devon polyposis syndrome (Allibone 1992)

    Bibliography

    • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
    • Schildhaus HU, Cavlar T, Binot E, Büttner R, Wardelmann E, Merkelbach-Bruse S. Inflammatory fibroid polyps harbour mutations in the platelet-derived growth factor receptor alpha (PDGFRA) gene. J Pathol. 2008 Oct;216(2):176-82.
    • Abraham SC. Distinguishing gastrointestinal stromal tumors from their mimics: an update. Adv Anat Pathol. 2007 May;14(3):178-88.
    • 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 Jan;28(1):107-14.
    • Makhlouf HR, Sobin LH. Inflammatory myofibroblastic tumors (inflammatory pseudotumors) of the gastrointestinal tract: how closely are they related to inflammatory fibroid polyps? Hum Pathol. 2002 Mar;33(3):307-15.
    • Kim MK, Higgins J, Cho EY, Ko YH, Oh YL. Expression of CD34, bcl-2, and kit in inflammatory fibroid polyps of the gastrointestinal tract. Appl Immunohistochem Mol Morphol. 2000 Jun;8(2):147-53.
    • Wille P, Borchard F. Fibroid polyps of intestinal tract are inflammatory-reactive proliferations of CD34-positive perivascular cells. Histopathology. 1998 Jun;32(6):498-502.
    • Hasegawa T, Yang P, Kagawa N, Hirose T, Sano T. CD34 expression by inflammatory fibroid polyps of the stomach. Mod Pathol. 1997 May;10(5):451-6.
    • Kolodziejczyk P, Yao T, Tsuneyoshi M. Inflammatory fibroid polyp of the stomach. A special reference to an immunohistochemical profile of 42 cases. Am J Surg Pathol. 1993 Nov;17(11):1159-68.
    • Allibone RO, Nanson JK, Anthony PP. Multiple and recurrent inflammatory fibroid polyps in a Devon family ('Devon polyposis syndrome'): an update. Gut. 1992 Jul;33(7):1004-5.
    • Daum O, Hatlova J, Mandys V, Grossmann P, Mukensnabl P, Benes Z, Michal M. Comparison of morphological, immunohistochemical, and molecular genetic features
      of inflammatory fibroid polyps (Vanek's tumors). Virchows Arch. 2010 May;456(5):491-7.
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