Benign tumors

Fibrous obliteration

Editorial Board Member: Catherine E. Hagen, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Raul S. Gonzalez, M.D.

Last author update: 28 April 2021
Last staff update: 15 October 2021

Copyright: 2002-2024,, Inc.

PubMed Search: Fibrous obliteration appendix

Raul S. Gonzalez, M.D.
Page views in 2023: 16,860
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Cite this page: Gonzalez RS. Fibrous obliteration. website. Accessed February 22nd, 2024.
Definition / general
  • Benign spindle cell proliferation replacing the lumen of the appendix
Essential features
  • Incidental, benign finding of the appendix
  • May obliterate mucosa and lumen
  • Wall becomes replaced with spindle cell proliferation and adipose tissue
ICD coding
  • ICD-10: K38.8 - other specified diseases of appendix
  • May occur just in tip or involve entire appendix
Clinical features
Gross description
  • Usually no gross tumor
  • Usually affects distal tip, may affect entire lumen
Microscopic (histologic) description
  • Lumen replaced by spindle cells in loose fibromyxoid background with chronic inflammatory cells (including eosinophils), hypertrophied nerve bundles, neuroendocrine cells, adipose cells and collagen
  • Loss of lymphoid follicles, mucosa and crypts
Microscopic (histologic) images

Contributed by Raul S. Gonzalez, M.D.
Obliterated lumen

Obliterated lumen

Adipose and spindle cells

Adipose and spindle cells

Bland spindle cells

Bland spindle cells

Superimposed acute appendicitis

Superimposed acute appendicitis

Positive stains
Sample pathology report
  • Appendix, appendectomy:
    • Appendix with fibrous obliteration
Differential diagnosis
Board review style question #1
    Which of the following is true about fibrous obliteration of the appendix?

  1. Can show marked cytologic atypia, mimicking sarcoma
  2. Generally only involves the base of the appendix
  3. May contain chronic inflammation and adipocytes
  4. Suggests an underlying diagnosis of neurofibromatosis type 1
Board review style answer #1
C. May contain chronic inflammation and adipocytes

Comment Here

Reference: Fibrous obliteration
Board review style question #2

    A young patient is diagnosed with acute appendicitis and the appendix specimen shows the pictured process occupying the lumen. Immunohistochemistry for what protein would be positive in this process?

  1. MUC4
  2. Myogenin
  3. S100
  4. SMA
Board review style answer #2
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