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Author: Mikael Häggström [notes 1]
Appendicitis may histopathologically be defined as neutrophilic infiltrates of the wall of the appendix in the correct clinical context.

See also: General notes on fixation



On this resource, the following formatting is used for comprehensiveness:

  • Minimal depth
  • (Moderate depth)
  • ((Comprehensive))

Gross processing

Acute suppurative appendicitis: The organ is enlarged and sausage-like (botuliform). This longitudinal section shows red inflamed mucosa with an irregular luminal surface. It was removed early in the disease, with no late complications like transmural necrosis, perforation, and abscess formation.

Standard sections if the appendix appears inflamed and there are no signs of malignancy.

Further information: Appendix

Microscopic evaluation

  • Evaluate depth of the inflammation.
  • Look for any perforation of the wall.
  • Look for cancerous cells (which may have caused the appendicitis). Further information: Appendix
  • (Attempt to specify the type of appendicitis as either of the following:)


Classification of acute appendicitis based on gross pathology and light microscopy characteristics[1]
Pattern Gross pathology Light microscopy Image Clinical significance
Acute intraluminal inflammation None visible
  • Only neutrophils in lumen
  • No ulceration or transmural inflammation
Probably none
Acute mucosal inflammation None visible
  • Neutrophils within mucosa, and possibly in submucosa
  • Mucosal ulceration
May be secondary to enteritis.
Suppurative acute appendicitis May be inapparent.
  • Dull mucosa
  • Congestion of surface vessels
  • Fibropurulent serosal exudate in late cases
  • Dilation of the appendix
  • Neutrophils in mucosa, submucosa and muscularis propria, potentially transmural.
  • Extensive inflammation
  • Commonly intramural abscesses
  • Possibly vascular thrombosis
  Can be presumed to be primary cause of symptoms
Gangrenous/necrotizing appendicitis
  • Friable wall
  • Purple, green or black color
  • Transmural inflammation
  • Necrotic areas
  • Extensive mucosal ulceration
Will perforate if untreated
Periappendicitis May be inapparent.
  • Serosa may be congested, dull and exudative
  • Serosal and subserosal inflammation, no further than outer muscularis propria to be called isolated.
  If isolated, probably secondary to other disease
Eosinophilic appendicitis None visible
  • >10 eosinophils/mm2 in muscularis propria.
  • No changes conforming to other types of appendicitis
Possibly parasitic, or eosinophilic enteritis.
Chronic appendicitis[2]
  • Fibrosis
  • Predominantly mononuclear infiltrate rather than neutrophilic.
  Should preferably correlate with long-term or recurrent symptoms.

Microscopy report

Should include, if detected:

  • Acute or chronic appendicitis
  • Depth of inflammation
  • Any abscess and\or perforation
  • Necrosis and\or ulceration, at least if transmural

(Classification into one or several types as per table above.)

Acute appendicitis and periappendicitis with transmural necrosis


  1. For a full list of contributors, see article history. Creators of images are attributed at the image description pages, seen by clicking on the images. See Patholines:Authorship for details.

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  1. Unless otherwise specified in rows, reference is:
    - Carr, Norman J. (2000). "The pathology of acute appendicitis ". Annals of Diagnostic Pathology 4 (1): 46–58. doi:10.1016/S1092-9134(00)90011-X. ISSN 10929134. 
  2. Sierakowski, Kyra; Pattichis, Andrew; Russell, Patrick; Wattchow, David (2016). "Unusual presentation of a familiar pathology: chronic appendicitis ". BMJ Case Reports: bcr2015212485. doi:10.1136/bcr-2015-212485. ISSN 1757-790X.