Difference between revisions of "Vermiform appendix"

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(+adenovirus)
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The appendix is a vestigial structure that is thought to have arisen from a larger cecum.  Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.<ref>{{cite book |author=Dawkins, R. |title=The Greatest Show on Earth: The Evidence for Evolution |publisher=Free Press |location= |year=2009 |pages=115 |edition=1st |isbn=978-1416594789 |oclc= |doi= |accessdate=}}</ref>  
The appendix is a vestigial structure that is thought to have arisen from a larger cecum.  Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.<ref>{{cite book |author=Dawkins, R. |title=The Greatest Show on Earth: The Evidence for Evolution |publisher=Free Press |location= |year=2009 |pages=115 |edition=1st |isbn=978-1416594789 |oclc= |doi= |accessdate=}}</ref>  


 
=Appendicitis=
==Acute appendicitis==
==Acute appendicitis==
===General===
===General===
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*May be perforated (best determined on gross).
*May be perforated (best determined on gross).
*+/-Fibrinous exudate.
*+/-Fibrinous exudate.
===Definition===
*[[Neutrophil]]s in the [[muscularis propria]].


===Microscopic===
===Microscopic===
Features:
Features:
* Neutrophils in the muscularis propria.
* Neutrophils in the muscularis propria - '''key feature'''.
* +/-Fecalith.
* +/- Vascular thrombosis (and [[necrosis]]) - known as ''gangrenous appendicitis''.<ref>URL: [http://emedicine.medscape.com/article/363818-overview http://emedicine.medscape.com/article/363818-overview]. Accessed on: 21 June 2010.</ref>
* +/- Vascular thrombosis (and [[necrosis]]) - known as ''gangrenous appendicitis''.<ref>URL: [http://emedicine.medscape.com/article/363818-overview http://emedicine.medscape.com/article/363818-overview]. Accessed on: 21 June 2010.</ref>
* +/- Findings suggestive of etiology - usu. absent:
** +/- Fecalith.
** +/- Viral inclusions (extremely rare)
*** See ''[[adenovirus appendicitis]]''.


===DDx===
====DDx====
*Mucinous tumour.
*Mucinous tumour.
*Neuroendocrine tumour.
*Neuroendocrine tumour.
*Granulomatous appendicitis.
*Granulomatous appendicitis.
*Crohn's disease of the appendix.
*Crohn's disease of the appendix.
==Adenovirus appendicitis==
===General===
*Rare type of appendicitis in children.
*Presents as run-of-the-mill acute appendicitis.
===Microscopic===
Features:<ref name=pmid17990936>{{cite journal |author=Grynspan D, Rabah R |title=Adenoviral appendicitis presenting clinically as acute appendicitis |journal=Pediatr. Dev. Pathol. |volume=11 |issue=2 |pages=138–41 |year=2008 |pmid=17990936 |doi=10.2350/07-06-0299.1 |url=}}</ref>
*Lymphoid hyperplasia - key feature.
*+/-Adenovirus inclusions; "smudge cells".
Notes:
*The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.<ref name=pmid17990936/>
Image:
*[http://wiki.medpedia.com/Image:Ab14.jpg?filetimestamp=20091014175858 Smudge cell (medpedia.com)].
===IHC===
*Adenovirus +ve = '''diagnostic'''.


==Granulomatous appendicitis==
==Granulomatous appendicitis==
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*Granulomas.
*Granulomas.


==Tumours of the appendix==
=Tumours of the appendix=
==Adenocarcinoma==
==Adenocarcinoma==
*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.
*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.
Line 139: Line 158:
*Nice review of stains in Pahlavan and Kanthan.<ref name=pmid15967038>{{cite journal |author=Pahlavan PS, Kanthan R |title=Goblet cell carcinoid of the appendix |journal=World J Surg Oncol |volume=3 |issue= |pages=36 |year=2005 |month=June |pmid=15967038 |pmc=1182398 |doi=10.1186/1477-7819-3-36 |url=http://wjso.com/content/3/1/36}}</ref>
*Nice review of stains in Pahlavan and Kanthan.<ref name=pmid15967038>{{cite journal |author=Pahlavan PS, Kanthan R |title=Goblet cell carcinoid of the appendix |journal=World J Surg Oncol |volume=3 |issue= |pages=36 |year=2005 |month=June |pmid=15967038 |pmc=1182398 |doi=10.1186/1477-7819-3-36 |url=http://wjso.com/content/3/1/36}}</ref>


==See also==
=See also=
*[[Colon]].
*[[Colon]].
*[[Gastrointestinal pathology]].
*[[Gastrointestinal pathology]].


==References==
=References=
{{reflist|2}}
{{reflist|2}}


[[Category:Gastrointestinal pathology]]
[[Category:Gastrointestinal pathology]]

Revision as of 14:19, 4 February 2011

The Vermiform appendix is, usually, just called appendix. Taking it out is the bread 'n butter of general surgery.

The appendix is a vestigial structure that is thought to have arisen from a larger cecum. Larger cecae are often seen in herbivores and thought to facilitate better digestion of plant matter.[1]

Appendicitis

Acute appendicitis

General

  • Bread 'n butter of general surgery.
  • Interesting factoid: appendicitis is considered protective against ulcerative colitis.[2][3]

Gross

Features:

  • Serosal surface dull.
  • May be perforated (best determined on gross).
  • +/-Fibrinous exudate.

Microscopic

Features:

  • Neutrophils in the muscularis propria - key feature.
  • +/- Vascular thrombosis (and necrosis) - known as gangrenous appendicitis.[4]
  • +/- Findings suggestive of etiology - usu. absent:

DDx

  • Mucinous tumour.
  • Neuroendocrine tumour.
  • Granulomatous appendicitis.
  • Crohn's disease of the appendix.

Adenovirus appendicitis

General

  • Rare type of appendicitis in children.
  • Presents as run-of-the-mill acute appendicitis.

Microscopic

Features:[5]

  • Lymphoid hyperplasia - key feature.
  • +/-Adenovirus inclusions; "smudge cells".

Notes:

  • The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.[5]

Image:

IHC

  • Adenovirus +ve = diagnostic.

Granulomatous appendicitis

Most common cause:

  • Yersinia appendicitis.[6]

DDx:[7]

  • Yersinia appendicitis.[6]
    • Yersinia = gram negative rod.
  • Other micro-organism (TB, fungus).
  • Crohn's disease.
  • Sarcoidosis.
  • Foreign body reaction.
  • Interval (delayed) appendectomy.

Microscopic

Features:

  • Granulomas.

Tumours of the appendix

Adenocarcinoma

Mucinous tumour

General

  • classification is controversial.
    • the controversy centres on whether to call all mucinous tumours outside of the appendix adenocarcinoma - regardless of whether they have atypia & show invasion.
  • in women - an ovarian primary must be excluded.
    • concurrent bilateral ovarian tumours suggests the tumour originated from the appendix and spread to the ovaries.

Classification[8]

  • benign - low grade mucinous tumour.
  • borderline - mucinous tumour of uncertain malignant potential or borderline mucinous tumour.
  • malignant - mucinous adenocarcinoma.

Five year survival[8]

5 year survival
LAMN 100%
LAMN ex-appy 86%
MACA 44%
  • LAMN = low-grade appendiceal mucinous neoplasm.
  • LAMN ex-appy = LAMN with extra-appendiceal spread.
  • MACA = mucinous adenocarcinoma.

Benign mucinous tumour

Micro.

  • Epithelium forms tufts - vaguely resemble serrations, i.e. the saw-tooth pattern in hyperplastic polyps.
  • Single layer of epithelium.
  • Mucin contained (inside appendix only).

Negatives

  • No marked nuclear atypia.
  • No invasion into the lamina propria.

Borderline mucinous tumour

Micro.

  • Same as benign, but mucin outside of the appendix.
  • Cells in mucin, i.e. cellular mucin.

Malignant mucinous tumour

Micro.

  • Marked nuclear pleomorphism.
  • Invasion into the wall.

Goblet cell carcinoid

General

  • AKA crypt cell carcinoma,[9] neuroendocrine tumour with goblet cell differentiation.
  • Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.[9]
  • Mixed (biphasic) tumour with endocrine and exocrine features.

Microscopic

Features:[10]

  • Mixed neuroendocrine-nonneuroendocrine tumour;[11] features of both carcinoid and adenocarcinoma.[10]
    • Archictecture: cells arranged in nests or clusters without a lumen.
    • Location: deep to the intestinal crypts (crypts of Lieberkühn); usually do not involve the mucosa.
    • Cytoplasm distended with mucin.
    • DNA: crescentic nucleus (similar to in signet-ring cells).
      • +/-Multinucleation.
      • +/-High mitotic rate.
      • Usually minimal nuclear atypia.

Images:

Stains

  • Mucin stains +ve:
    • Mucicarmine, perodic acid-Schiff diastase (PAS-D), alician blue.

IHC

  • Classic neuroendocrine markers:
    • Synaptophysin +ve.
    • Chromogranin +ve.
  • S100 +ve.
  • NSE +ve.
  • Serotonin +ve.

Keratins:

  • Usually CK20 +ve > CK7 +ve.
  • CEA +ve (membrane).

Notes:

  • Nice review of stains in Pahlavan and Kanthan.[10]

See also

References

  1. ↑ Dawkins, R. (2009). The Greatest Show on Earth: The Evidence for Evolution (1st ed.). Free Press. pp. 115. ISBN 978-1416594789.
  2. ↑ Beaugerie, L.; Sokol, H. (Aug 2009). "Appendicitis, not appendectomy, is protective against ulcerative colitis, both in the general population and first-degree relatives of patients with IBD.". Inflamm Bowel Dis. doi:10.1002/ibd.21064. PMID 19685454.
  3. ↑ Timmer, A.; Obermeier, F. (2009). "Reduced risk of ulcerative colitis after appendicectomy.". BMJ 338: b225. PMID 19273505.
  4. ↑ URL: http://emedicine.medscape.com/article/363818-overview. Accessed on: 21 June 2010.
  5. ↑ 5.0 5.1 Grynspan D, Rabah R (2008). "Adenoviral appendicitis presenting clinically as acute appendicitis". Pediatr. Dev. Pathol. 11 (2): 138–41. doi:10.2350/07-06-0299.1. PMID 17990936.
  6. ↑ 6.0 6.1 Lamps LW, Madhusudhan KT, Greenson JK, et al. (April 2001). "The role of Yersinia enterocolitica and Yersinia pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study". Am. J. Surg. Pathol. 25 (4): 508–15. PMID 11257626.
  7. ↑ http://granuloma.homestead.com/appendicitis.html
  8. ↑ 8.0 8.1 Misdraji J, Yantiss RK, Graeme-Cook FM, Balis UJ, Young RH (August 2003). "Appendiceal mucinous neoplasms: a clinicopathologic analysis of 107 cases". Am. J. Surg. Pathol. 27 (8): 1089–103. PMID 12883241. http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=27&issue=8&spage=1089.
  9. ↑ 9.0 9.1 van Eeden S, Offerhaus GJ, Hart AA, et al. (December 2007). "Goblet cell carcinoid of the appendix: a specific type of carcinoma". Histopathology 51 (6): 763–73. doi:10.1111/j.1365-2559.2007.02883.x. PMID 18042066.
  10. ↑ 10.0 10.1 10.2 Pahlavan PS, Kanthan R (June 2005). "Goblet cell carcinoid of the appendix". World J Surg Oncol 3: 36. doi:10.1186/1477-7819-3-36. PMC 1182398. PMID 15967038. http://wjso.com/content/3/1/36. Cite error: Invalid <ref> tag; name "pmid15967038" defined multiple times with different content Cite error: Invalid <ref> tag; name "pmid15967038" defined multiple times with different content
  11. ↑ Volante M, Righi L, Asioli S, Bussolati G, Papotti M (August 2007). "Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms". Virchows Arch. 451 Suppl 1: S61–9. doi:10.1007/s00428-007-0447-y. PMID 17684764.
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