Mesenchymal tumors

Idiopathic retroperitoneal fibrosis

Last author update: 26 February 2021
Last staff update: 28 April 2022

Copyright: 2003-2024,, Inc.

PubMed Search: Retroperitoneal fibrosis colon

Raul S. Gonzalez, M.D.
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Cite this page: Gonzalez RS. Idiopathic retroperitoneal fibrosis. website. Accessed May 19th, 2024.
Definition / general
  • Nonneoplastic fibrosis that develops in retroperitoneum and may encroach upon colon
Essential features
  • Benign fibrosing process of the retroperitoneum that can rarely involve the gastrointestinal tract secondarily
  • Some cases belong to the spectrum of IgG4 related disease
  • Also called Ormond disease, idiopathic retroperitoneal fibrosis
  • Arises in retroperitoneum, often at aortic bifurcation
  • Gastrointestinal tract involvement is rare
  • IgG4 positive plasma cells implicated as a causative factor (Am J Surg Pathol 2009;33:1833)
  • Can also be caused by methysergide or lymphoma or may be idiopathic
Clinical features
  • Increased serum IgG and IgG4 in patients with IgG4 related disease
Radiology images

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Retroperitoneal mass enveloping aorta

Case reports
Gross description
  • Poorly circumscribed fibrotic mass
Microscopic (histologic) description
  • Storiform fibrotic process infiltrated by eosinophils and IgG4 positive plasma cells (which may be sparse)
  • May show obliterative phlebitis, fat necrosis
  • Similar findings may be observed in lymph nodes (Am J Clin Pathol 1996;105:430)
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.
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Fibrosis and inflammation

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Fibrosis involving ureter

Positive stains
  • IgG4 (in plasma cells)
Sample pathology report
  • Transverse colon and adjacent soft tissue mass, excision:
    • Prominent bland fibrotic process involving soft tissue and focally extending into colon wall (see comment)
    • Negative for malignancy.
    • Margins of resection unremarkable.
    • Comment: The soft tissue fibrosis shows a storiform pattern and contains abundant chronic inflammation. An immunostain for IgG4 highlights numerous plasma cells. The overall findings are most consistent with idiopathic retroperitoneal fibrosis.
Differential diagnosis
Board review style question #1
Which of the following is true about idiopathic retroperitoneal fibrosis?

  1. Colon is often secondarily involved
  2. Most patients present with lower gastrointestinal bleeding
  3. Numerous IgG4 positive plasma cells are seen histologically
  4. Obliterative arteritis can be seen
Board review style answer #1
C. Numerous IgG4 positive plasma cells are seen histologically

Comment Here

Reference: Idiopathic retroperitoneal fibrosis
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