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collagenous colitis

Monday 15 December 2003

PO

Definition: Collagenous colitis is a subtype of microscopic colitis .

Images

- collagenous colitis

Microscopy

- Patchy thickening of subepithelial basement membrane

  • thickness : 10 microns or more / 0.01 mm (thickest in transverse colon);
  • often spares rectosigmoid;
  • lower border of collagen is irregular,
  • extends into lamina propria and encircles capillaries,
  • may be difficult to measure

- Also increased chronic inflammatory cells (lymphocytes, plasma cells, eosinophils) in lamina propria and within surface epithelium (20+ lymphocytes per 100 epithelial cells)
- Epithelial damage is demonstrated by loss of mucin and irregular orientation of nuclei
- Usually no neutrophilic infiltration, no atrophy, no mucosal architectural distortion
6+ intraepithelial lymphocytes per 100 epithelial cells in terminal ileum is 98% specific and 50-60% sensitive for collagenous/lymphocytic colitis (Am J Surg Pathol 2002;26:1484)
- Increased connective tissue growth factor expression; may be end stage mediator of local fibrosis (Histopathology 2010;57:427)

Diagnosis

- do not base on thickness of collagen, but distorted superficial cell arrangement with areas of epithelial denudation and inflammatory cells in superficial epithelium and the lamina propria;

  • Lazenby’s statement: "Focusing solely on the collagen band can result in both over- and underdiagnosis" (Am J Clin Pathol 2008;130:375)

Differential diagnosis

- Chronic ischemic damage: fibrosis in lamina propria
- Lymphocytic colitis: no collagen
- Nonspecific changes
- Scleroderma: affects muscularis propria
- Solitary rectal ulcer syndrome: mucosal architectural distortion, variable collagen deposits but no intraepithelial lymphocytes
- Tangential sectioning of subepithelial basement membrane (lacks inflammation)

Variants

- pseudomembranous collagenous colitis (14508399)

References

- Goldstein NS, Gyorfi T. Focal lymphocytic colitis and collagenous colitis: patterns of Crohn’s colitis? Am J Surg Pathol. 1999 Sep;23(9):1075-81. PMID: 10478667