Vermiform appendix
Jump to navigation
Jump to search
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:
- Symptomatic Meckel diverticulum.
- Epiploic appendagitis.
- 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:
- +/- Fecalith.
- +/- Viral inclusions (extremely rare)
Images:
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.
Enterobius vermicularis
Main article: Enterobius vermicularis
- AKA pinworm.
General
- May be found in the appendix.
- The incidence is higher in normal appendices than inflamed ones.[6][7]
Microscopic
Features:
- Usu. the appendiceal wall has no inflammation, i.e. there is no appendicitis.[6][7]
- Enterobius vermicularis organisms.
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
Periappendicitis
General
Definition: inflammation of tissues around the (vermiform) appendix.[11]
- May be seen in association of appendicitis or alone.
Microscopic
Features:
- Acute inflammation of the serosa.
- Neutrophils in the serosa.
Tumours of the appendix
Adenocarcinoma
- Like colorectal adenocarcinoma - see colorectal tumours.
Mucinous tumours of the appendix
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.
- Malignant - mucinous adenocarcinoma.
Five year survival (in a series of 107 cases):[14]
| Tumour | Five year survival |
|---|---|
| LAMN | 100% |
| LAMN extra-appendiceal spread | 86% |
| MACA | 44% |
- LAMN = low-grade appendiceal mucinous neoplasm.
- LAMN extra-appendiceal = low-grade appendiceal mucinous neoplasm with extra-appendiceal spread.
- MACA = mucinous adenocarcinoma of the appendix.
Microscopic
Low-grade appendiceal mucinous neoplasm
- AKA benign mucinous tumour of the appendix.
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.
Low-grade appendiceal mucinous neoplasm with extra-appendiceal spread
- AKA mucinous borderline tumour of the appendix.
Microscopic:
- Same as LAMN but mucin outside of the appendix.
- Cells in mucin, i.e. cellular mucin.
Mucinous adenocarcinoma of the appendix
- AKA malignant mucinous tumour of the appendix.
Microscopic:
- Marked nuclear pleomorphism.
- Invasion into the appendiceal 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 neuroendocrine tumour, abbreviated 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:
- Chromogranin A -ve/+ve.
- Synaptophysin +ve.
See: neuroendocrine tumours.
See also
References
- ↑ Dawkins, R. (2009). The Greatest Show on Earth: The Evidence for Evolution (1st ed.). Free Press. pp. 115. ISBN 978-1416594789.
- ↑ 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.
- ↑ Timmer, A.; Obermeier, F. (2009). "Reduced risk of ulcerative colitis after appendicectomy.". BMJ 338: b225. PMID 19273505.
- ↑ URL: http://emedicine.medscape.com/article/363818-overview. Accessed on: 21 June 2010.
- ↑ 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.
- ↑ 6.0 6.1 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
- ↑ 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.
- ↑ 8.0 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.
- ↑ http://granuloma.homestead.com/appendicitis.html
- ↑ URL: http://www.cdc.gov/ncidod/dvbid/plague/p1.htm. Accessed on: 30 June 2011.
- ↑ URL: http://www.medilexicon.com/medicaldictionary.php?t=66889. Accessed on: 1 June 2011.
- ↑ 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.
- ↑ O'Neil, MB.; Moore, DB. (Sep 1977). "Periappendicitis: Clinical reality or pathologic curiosity?". Am J Surg 134 (3): 356-7. PMID 900337.
- ↑ 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.
- ↑ 15.0 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.
- ↑ 16.0 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 - ↑ 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.
- ↑ 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.
- ↑ 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.