Difference between revisions of "Vermiform appendix"

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The '''Vermiform appendix''' is, usually, just called ''appendix''.  Taking it out is the bread 'n butter of general surgery.
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.<ref>{{cite book |author=Dawkins, R. |title=The Greatest Show on Earth: The Evidence for Evolution |publisher=Free Press |location= |year=2009 |pages= |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>  




Revision as of 04:48, 8 July 2010

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]


Acute appendicitis

General

  • Bread 'n butter of general surgery.

Gross

Features:

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

Definition

Microscopic

Features:

  • Neutrophils in the muscularis propria.
  • +/-Fecalith.
  • +/- Vascular thrombosis (and necrosis) - known as gangrenous appendicitis.[2]

DDx

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

Granulomatous appendicitis

Most common cause:

  • Yersinia appendicitis.[3]

DDx:[4]

  • Yersinia appendicitis.[3]
    • 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[5]

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

Five year survival[5]

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

  • Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoid.[6]
  • AKA crypt cell carcinoma - probably a better descriptor.[6]
  • Mixed (biphasic) tumour with endocrine and exocrine features.

Histology

Features:[7]

  • Mixed neuroendocrine-nonneuroendocrine tumour;[8] features of both carcinoid and adenocarcinoma.[7]
    • 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.

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.[7]

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. ↑ URL: http://emedicine.medscape.com/article/363818-overview. Accessed on: 21 June 2010.
  3. ↑ 3.0 3.1 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.
  4. ↑ http://granuloma.homestead.com/appendicitis.html
  5. ↑ 5.0 5.1 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.
  6. ↑ 6.0 6.1 PMID 18042066.
  7. ↑ 7.0 7.1 7.2 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
  8. ↑ 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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