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Author: Mikael Häggström [note 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

Standard sections if the appendix appears inflamed and there are no signs of malignancy. Describe abnormal signs including:

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, obliterating normal histological structures
  • 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.

Further workup

(In acute suppurative appendicitis, still look for any periappendicitis. Also look by the lumen for parasites.)

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.)

(Appendix, resection (or appendectomy):)
Acute (suppurative) appendicitis (and periappendicitis) with transmural necrosis and perforation.


  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. 

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