Difference between revisions of "Vermiform appendix"

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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=
=Normal=
==Acute appendicitis==
==Normal vermiform appendix==
===General===
===General===
*Bread 'n butter of general surgery.
*Seen in:
*Interesting factoid: appendicitis is considered protective against [[ulcerative colitis]].<ref name=pmid19685454>{{Cite journal  | last1 = Beaugerie | first1 = L. | last2 = Sokol | first2 = H. | title = Appendicitis, not appendectomy, is protective against ulcerative colitis, both in the general population and first-degree relatives of patients with IBD. | journal = Inflamm Bowel Dis | volume =  | issue =  | pages =  | month = Aug | year = 2009 | doi = 10.1002/ibd.21064 | PMID = 19685454 }}</ref><ref name=pmid19273505>{{Cite journal  | last1 = Timmer | first1 = A. | last2 = Obermeier | first2 = F. | title = Reduced risk of ulcerative colitis after appendicectomy. | journal = BMJ | volume = 338 | issue =  | pages = b225 | month =  | year = 2009 | doi =  | PMID = 19273505 }}</ref>
**Right hemicolectomies.
***[[colorectal carcinoma|Colon cancer]].
***[[Crohn's disease]].
**Surgeries for ovarian mucinous tumours.


===Gross===
===Gross===
Features:
*Shiny serosal surface.
*Serosal surface dull.
**No exudate.
*May be perforated (best determined on gross).
*Normal diameter.
*+/-Fibrinous exudate.
**6.6 +/- 1.5 mm -- based on CT.<ref name=pmid21344807>{{Cite journal  | last1 = Charoensak | first1 = A. | last2 = Pongpornsup | first2 = S. | last3 = Suthikeeree | first3 = W. | title = Wall thickness and outer diameter of the normal appendix in adults using 64 slices multidetector CT. | journal = J Med Assoc Thai | volume = 93 | issue = 12 | pages = 1437-42 | month = Dec | year = 2010 | doi =  | PMID = 21344807 }}</ref>


===Microscopic===
===Microscopic===
Features:
Features:
* Neutrophils in the muscularis propria - '''key feature'''.
*+/-Lymphoid hyperplasia - mucosa or submucosa.
* +/- 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>
*Normal colorectal-type mucosa.
* +/- Findings suggestive of etiology - usu. absent:
*Fatty submucosa.
** +/- Fecalith.
*Benign smooth muscle.
** +/- Viral inclusions (extremely rare)
*Serosa.
*** See ''[[adenovirus appendicitis]]''.


====DDx====
Negatives:
*Mucinous tumour.
*No [[neutrophil]]s in the muscularis propria.
*Neuroendocrine tumour.
*No lesion in appendiceal tip.
*Granulomatous appendicitis.
*No serosal inflammation ([[periappendicitis]]).
*Crohn's disease of the appendix.
*No organisms in the appendiceal lumen, e.g. [[Enterobius vermicularis]].


==Adenovirus appendicitis==
DDx:
===General===
*[[Adenovirus appendicitis]].
*Rare type of appendicitis in children.
*[[Cryptosporidiosis]].
*Presents as run-of-the-mill acute appendicitis.
*Mild colitis.


===Microscopic===
===Sign out===
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>
<pre>
*Lymphoid hyperplasia - key feature.
VERMIFORM APPENDIX WITHIN NORMAL LIMITS.
*+/-Adenovirus inclusions; "smudge cells".
</pre>


Notes:
Note:
*The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.<ref name=pmid17990936/>
*This is for a normal appendix within a larger operation. The article ''[[negative appendectomy]]'' deals with a normal appearing appendix that was removed for presumed appendicitis.


Image:
==Negative appendectomy==
*[http://wiki.medpedia.com/Image:Ab14.jpg?filetimestamp=20091014175858 Smudge cell (medpedia.com)].
{{Main|Negative appendectomy}}
An appendectomy done for presumed [[acute appendicitis]] that is pathologically within normal limits


===IHC===
=Inflammatory pathologies=
*Adenovirus +ve = '''diagnostic'''.
==Acute appendicitis==
{{Main|Acute appendicitis}}


==Granulomatous appendicitis==
==Adenovirus appendicitis==
Most common cause:
{{Main|Adenovirus appendicitis}}
*Yersinia appendicitis.<ref name=pmid11257626>{{cite journal |author=Lamps LW, Madhusudhan KT, Greenson JK, ''et al.'' |title=The role of Yersinia enterocolitica and Yersinia pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study |journal=Am. J. Surg. Pathol. |volume=25 |issue=4 |pages=508–15 |year=2001 |month=April |pmid=11257626 |doi= |url=}}</ref>


DDx:<ref>[http://granuloma.homestead.com/appendicitis.html http://granuloma.homestead.com/appendicitis.html]</ref>
==Enterobius vermicularis==
*Yersinia appendicitis.<ref name=pmid11257626>{{cite journal |author=Lamps LW, Madhusudhan KT, Greenson JK, ''et al.'' |title=The role of Yersinia enterocolitica and Yersinia pseudotuberculosis in granulomatous appendicitis: a histologic and molecular study |journal=Am. J. Surg. Pathol. |volume=25 |issue=4 |pages=508–15 |year=2001 |month=April |pmid=11257626 |doi= |url=}}</ref>  
{{Main|Enterobius vermicularis}}
**Yersinia = gram negative rod.
*[[AKA]] ''pinworm''.
*Other micro-organism (TB, fungus).
===General===
*[[Crohn's disease]].
*May be found in the appendix.
*[[Sarcoidosis]].
*The incidence is higher in normal appendices than inflamed ones.<ref name=pmid1853157>{{Cite journal  | last1 = Wiebe | first1 = BM. | title = Appendicitis and Enterobius vermicularis. | journal = Scand J Gastroenterol | volume = 26 | issue = 3 | pages = 336-8 | month = Mar | year = 1991 | doi =  | PMID = 1853157 }}</ref><ref name=pmid7945067/>
*Foreign body reaction.
*Clinically mimics appendicitis.<ref>{{cite journal |author=Ariyarathenam AV, Nachimuthu S, Tang TY, Courtney ED, Harris SA, Harris AM |title=Enterobius vermicularis infestation of the appendix and management at the time of laparoscopic appendectomy: case series and literature review |journal=Int J Surg |volume=8 |issue=6 |pages=466–9 |year=2010 |pmid=20637320 |doi=10.1016/j.ijsu.2010.06.007 |url=}}</ref>
*Interval (delayed) appendectomy.


===Microscopic===
===Microscopic===
Features:
Features:
*Granulomas.
*Usu. the appendiceal wall has no inflammation, i.e. there is no appendicitis.<ref name=pmid1853157/><ref name=pmid7945067>{{Cite journal  | last1 = Dahlstrom | first1 = JE. | last2 = Macarthur | first2 = EB. | title = Enterobius vermicularis: a possible cause of symptoms resembling appendicitis. | journal = Aust N Z J Surg | volume = 64 | issue = 10 | pages = 692-4 | month = Oct | year = 1994 | doi = | PMID = 7945067 }}</ref>
 
*''[[Enterobius vermicularis]]'' organisms.
=Tumours of the appendix=
==Adenocarcinoma==
*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.


==Mucinous tumour==
====Image====
General
<gallery>
*classification is controversial.
Image:Enterobius_-_very_low_mag.jpg | Enterobius - very low mag. (WC/Nephron)
**the controversy centres on whether to call all mucinous tumours outside of the appendix adenocarcinoma - regardless of whether they have atypia & show invasion.
Image:Enterobius_-_high_mag.jpg | Enterobius - high mag. (WC/Nephron)
*in women - an ovarian primary must be excluded.
Image:Pinworms_in_the_Appendix_%281%29.jpg | Pinworm (WC/Uthman)
**concurrent ''bilateral'' ovarian tumours suggests the tumour originated from the appendix and spread to the ovaries.
</gallery>


Classification<ref name=pmid12883241>{{cite journal |author=Misdraji J, Yantiss RK, Graeme-Cook FM, Balis UJ, Young RH |title=Appendiceal mucinous neoplasms: a clinicopathologic analysis of 107 cases |journal=Am. J. Surg. Pathol. |volume=27 |issue=8 |pages=1089–103 |year=2003 |month=August |pmid=12883241 |doi= |url=http://meta.wkhealth.com/pt/pt-core/template-journal/lwwgateway/media/landingpage.htm?issn=0147-5185&volume=27&issue=8&spage=1089}}</ref>
==Granulomatous appendicitis==
*benign - ''low grade mucinous tumour''.
{{Main|Granulomatous appendicitis}}
*borderline - ''mucinous tumour of uncertain malignant potential'' or ''borderline mucinous tumour''.
*malignant - ''mucinous adenocarcinoma''.


Five year survival<ref name=pmid12883241/>
==Inflammatory bowel disease==
{| class="wikitable"
: See ''[[Inflammatory bowel disease]]''.
| ||'''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===
==Periappendicitis==
Micro.
===General===
*Epithelium forms ''tufts'' - vaguely resemble ''serrations'', i.e. the ''saw-tooth'' pattern in hyperplastic polyps.
Definition: inflammation of tissues around the (vermiform) appendix.<ref>URL: [http://www.medilexicon.com/medicaldictionary.php?t=66889 http://www.medilexicon.com/medicaldictionary.php?t=66889]. Accessed on: 1 June 2011.</ref>
*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==
*May be seen in association of appendicitis or alone.
===General===
**With appendicitis it is suggestive of perforation.
*[[AKA]] '''crypt cell carcinoma''',<ref name=pmid18042066>{{cite journal |author=van Eeden S, Offerhaus GJ, Hart AA, ''et al.'' |title=Goblet cell carcinoid of the appendix: a specific type of carcinoma |journal=Histopathology |volume=51 |issue=6 |pages=763–73 |year=2007 |month=December |pmid=18042066 |doi=10.1111/j.1365-2559.2007.02883.x |url=}}</ref> '''neuroendocrine tumour with goblet cell differentiation.
**Without concurrent appendicitis it is suggestive of another abdominal pathology.<ref name=pmid2349982>{{Cite journal | last1 = Fink | first1 = AS. | last2 = Kosakowski | first2 = CA. | last3 = Hiatt | first3 = JR. | last4 = Cochran | first4 = AJ. | title = Periappendicitis is a significant clinical finding. | journal = Am J Surg | volume = 159 | issue = 6 | pages = 564-8 | month = Jun | year = 1990 | doi = | PMID = 2349982 }}</ref><ref>{{Cite journal | last1 = O'Neil | first1 = MB. | last2 = Moore | first2 = DB. | title = Periappendicitis: Clinical reality or pathologic curiosity? | journal = Am J Surg | volume = 134 | issue = 3 | pages = 356-7 | month = Sep | year = 1977 | doi = | PMID = 900337 }}</ref>
*Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.<ref name=pmid18042066>{{cite journal |author=van Eeden S, Offerhaus GJ, Hart AA, ''et al.'' |title=Goblet cell carcinoid of the appendix: a specific type of carcinoma |journal=Histopathology |volume=51 |issue=6 |pages=763–73 |year=2007 |month=December |pmid=18042066 |doi=10.1111/j.1365-2559.2007.02883.x |url=}}</ref>
*Mixed (biphasic) tumour with endocrine and exocrine features.


===Microscopic===
===Microscopic===
Features:<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>
Features:
*Mixed neuroendocrine-nonneuroendocrine tumour;<ref name=pmid17684764>{{cite journal |author=Volante M, Righi L, Asioli S, Bussolati G, Papotti M |title=Goblet cell carcinoids and other mixed neuroendocrine/nonneuroendocrine neoplasms |journal=Virchows Arch. |volume=451 Suppl 1 |issue= |pages=S61–9 |year=2007 |month=August |pmid=17684764 |doi=10.1007/s00428-007-0447-y |url=}}</ref> features of both ''carcinoid'' and ''adenocarcinoma.<ref name=pmid15967038>PMID 15967038.</ref>
*Acute inflammation of the serosa.
**Archictecture: cells arranged in nests or clusters without a lumen.
**[[Neutrophil]]s in the serosa.
**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:
DDx:
*[http://commons.wikimedia.org/wiki/File:Goblet_cell_carcinoid_-2-_very_high_mag.jpg GCC - very high mag. (WC)].
*[[Acute appendicitis]].
*[http://commons.wikimedia.org/wiki/File:Goblet_cell_carcinoid_-_very_low_mag.jpg GCC - very low mag. (WC)].


===Stains===
=Tumours of the appendix=
*Mucin stains +ve:
==Adenocarcinoma==
**Mucicarmine, perodic acid-Schiff diastase (PAS-D), alician blue.
*Like ''colorectal adenocarcinoma'' - see ''[[colorectal tumours]]''.
 
====IHC====
*Classic neuroendocrine markers:
**Synaptophysin +ve.
**Chromogranin +ve.
*S100 +ve.
*NSE +ve.
*Serotonin +ve.


Keratins:
==Mucinous tumours of the appendix==
*Usually CK20 +ve > CK7 +ve.
{{Main|Mucinous tumours of the appendix}}
This grouping includes ''mucinous cystadenoma'' and ''mucinous cystadenocarcinoma''.


*CEA +ve (membrane).
==Goblet cell adenocarcinoma==
{{Main|Goblet cell adenocarcinoma}}
*Previously known as ''goblet cell carcinoid''.


Notes:
==Neuroendocrine tumour of the appendix==
*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>
*Previously known as ''appendiceal carcinoid''.
*[[AKA]] ''appendiceal neuroendocrine tumour'', abbreviated ''appendiceal NET''.  
{{Main|Neuroendocrine tumour of the appendix}}


=See also=
=See also=
Line 166: Line 123:


[[Category:Gastrointestinal pathology]]
[[Category:Gastrointestinal pathology]]
[[Category:Vermiform appendix]]

Latest revision as of 15:11, 4 December 2023

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]

Normal

Normal vermiform appendix

General

Gross

  • Shiny serosal surface.
    • No exudate.
  • Normal diameter.
    • 6.6 +/- 1.5 mm -- based on CT.[2]

Microscopic

Features:

  • +/-Lymphoid hyperplasia - mucosa or submucosa.
  • Normal colorectal-type mucosa.
  • Fatty submucosa.
  • Benign smooth muscle.
  • Serosa.

Negatives:

DDx:

Sign out

VERMIFORM APPENDIX WITHIN NORMAL LIMITS.

Note:

  • This is for a normal appendix within a larger operation. The article negative appendectomy deals with a normal appearing appendix that was removed for presumed appendicitis.

Negative appendectomy

An appendectomy done for presumed acute appendicitis that is pathologically within normal limits

Inflammatory pathologies

Acute appendicitis

Adenovirus appendicitis

Enterobius vermicularis

General

  • May be found in the appendix.
  • The incidence is higher in normal appendices than inflamed ones.[3][4]
  • Clinically mimics appendicitis.[5]

Microscopic

Features:

Image

Granulomatous appendicitis

Inflammatory bowel disease

See Inflammatory bowel disease.

Periappendicitis

General

Definition: inflammation of tissues around the (vermiform) appendix.[6]

  • 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.[7][8]

Microscopic

Features:

  • Acute inflammation of the serosa.

DDx:

Tumours of the appendix

Adenocarcinoma

Mucinous tumours of the appendix

This grouping includes mucinous cystadenoma and mucinous cystadenocarcinoma.

Goblet cell adenocarcinoma

  • Previously known as goblet cell carcinoid.

Neuroendocrine tumour of the appendix

  • Previously known as appendiceal carcinoid.
  • AKA appendiceal neuroendocrine tumour, abbreviated appendiceal NET.

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. Charoensak, A.; Pongpornsup, S.; Suthikeeree, W. (Dec 2010). "Wall thickness and outer diameter of the normal appendix in adults using 64 slices multidetector CT.". J Med Assoc Thai 93 (12): 1437-42. PMID 21344807.
  3. 3.0 3.1 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
  4. 4.0 4.1 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.
  5. Ariyarathenam AV, Nachimuthu S, Tang TY, Courtney ED, Harris SA, Harris AM (2010). "Enterobius vermicularis infestation of the appendix and management at the time of laparoscopic appendectomy: case series and literature review". Int J Surg 8 (6): 466–9. doi:10.1016/j.ijsu.2010.06.007. PMID 20637320.
  6. URL: http://www.medilexicon.com/medicaldictionary.php?t=66889. Accessed on: 1 June 2011.
  7. 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.
  8. O'Neil, MB.; Moore, DB. (Sep 1977). "Periappendicitis: Clinical reality or pathologic curiosity?". Am J Surg 134 (3): 356-7. PMID 900337.