Difference between revisions of "Vermiform appendix"

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{{Main|Neuroendocrine tumour}}
{{Main|Neuroendocrine tumour}}
*Previously known as ''appendiceal carcinoid''.
*Previously known as ''appendiceal carcinoid''.
*[[AKA]] ''appendiceal NET''.
===General===
===General===
*Most common tumour of the appendix.<ref name=PCPBoD8_435>{{Ref PCPBoD8|435}}</ref>
*Most common tumour of the appendix.<ref name=PCPBoD8_435>{{Ref PCPBoD8|435}}</ref>

Revision as of 14:25, 30 March 2012

The vermiform appendix, usually just appendix, is a little thingy that is attached to the cecum. 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]

Inflammatory pathologies

Acute appendicitis

General

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

Short clinical DDx:

  • GI tract:
  • Gynecologic tract:
    • Ectopic pregnancy.
    • Ruptured ovarian cyst.
    • Ovarian torsion.
      • Pelvic inflammatory disease.

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:

Images:

DDx

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.

Enterobius vermicularis

Main article: Enterobius vermicularis

General

  • May be found in the appendix.
  • The incidence is higher in normal appendices than inflamed ones.[6][7]

Microscopic

Features:

Granulomatous appendicitis

Most common cause:

  • Yersinia appendicitis.[8]

DDx:[9]

  • Yersinia appendicitis.[8]
    • Yersinia = gram negative rod (red on Gram stain).
    • "Safety pin"-like appearance[10] - approximately 0.5 micrometers diameter x 2 micrometers length.
  • Other micro-organism (TB, fungus).
  • Crohn's disease.
  • Sarcoidosis.
  • Foreign body reaction.
  • Interval (delayed) appendectomy.

Microscopic

Features:

  • Granulomas.
  • +/-"Safety pin"-like organisms (Yersinia).

Image(s):

Inflammatory bowel disease

See Inflammatory bowel disease.

Periappendicitis

General

Definition: inflammation of tissues around the (vermiform) appendix.[11]

  • May be seen in association of appendicitis or alone.
    • With appendicitis it is suggestive of perforation.
    • Without concurrent appendicitis it is suggestive of another abdominal pathology.[12][13]

Microscopic

Features:

  • Acute inflammation of the serosa.

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:[14]

  • Benign - low grade mucinous tumour.
  • Borderline - mucinous tumour of uncertain malignant potential or borderline mucinous tumour.
  • Balignant - mucinous adenocarcinoma.

Five year survival (in a series of 107 cases):[14]

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

Benign mucinous tumour

Microscopic:

  • 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

Microscopic:

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

Malignant mucinous tumour

Microscopic:

  • Marked nuclear pleomorphism.
  • Invasion into the wall.

Goblet cell carcinoid

General

  • AKA crypt cell carcinoma,[15] neuroendocrine tumour with goblet cell differentiation.
  • Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.[15]
  • Mixed (biphasic) tumour with endocrine and exocrine features.

Microscopic

Features:[16]

  • Mixed neuroendocrine-nonneuroendocrine tumour;[17] features of both carcinoid and adenocarcinoma.[16]
    • 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.[16]

Neuroendocrine tumour of the appendix

Main article: Neuroendocrine tumour
  • Previously known as appendiceal carcinoid.
  • AKA appendiceal NET.

General

  • Most common tumour of the appendix.[18]

Size matters in appendiceal NETs:[19]

  • <1.0 cm - do not metastasize.
  • 1.0-2.0 cm - rarely metastasize.

Microscopic

Features:

IHC

Features:

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 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
  7. ↑ 7.0 7.1 Dahlstrom, JE.; Macarthur, EB. (Oct 1994). "Enterobius vermicularis: a possible cause of symptoms resembling appendicitis.". Aust N Z J Surg 64 (10): 692-4. PMID 7945067.
  8. ↑ 8.0 8.1 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.
  9. ↑ http://granuloma.homestead.com/appendicitis.html
  10. ↑ URL: http://www.cdc.gov/ncidod/dvbid/plague/p1.htm. Accessed on: 30 June 2011.
  11. ↑ URL: http://www.medilexicon.com/medicaldictionary.php?t=66889. Accessed on: 1 June 2011.
  12. ↑ Fink, AS.; Kosakowski, CA.; Hiatt, JR.; Cochran, AJ. (Jun 1990). "Periappendicitis is a significant clinical finding.". Am J Surg 159 (6): 564-8. PMID 2349982.
  13. ↑ O'Neil, MB.; Moore, DB. (Sep 1977). "Periappendicitis: Clinical reality or pathologic curiosity?". Am J Surg 134 (3): 356-7. PMID 900337.
  14. ↑ 14.0 14.1 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.
  15. ↑ 15.0 15.1 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.
  16. ↑ 16.0 16.1 16.2 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
  17. ↑ 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.
  18. ↑ Mitchell, Richard; Kumar, Vinay; Fausto, Nelson; Abbas, Abul K.; Aster, Jon (2011). Pocket Companion to Robbins & Cotran Pathologic Basis of Disease (8th ed.). Elsevier Saunders. pp. 435. ISBN 978-1416054542.
  19. ↑ Modlin, IM.; Lye, KD.; Kidd, M. (Feb 2003). "A 5-decade analysis of 13,715 carcinoid tumors.". Cancer 97 (4): 934-59. doi:10.1002/cncr.11105. PMID 12569593.
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