Difference between revisions of "Vermiform appendix"
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Revision as of 13:22, 27 September 2013
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
- Seen in:
- Right hemicolectomies.
- Surgeries for ovarian mucinous tumours.
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:
- No neutrophils in the muscularis propria.
- No lesion in appendiceal tip.
- No serosal inflammation (periappendicitis).
- No organisms in the appendiceal lumen, e.g. Enterobius vermicularis.
DDx:
- Adenovirus appendicitis.
- Cryptosporidiosis.
- Mild colitis.
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VERMIFORM APPENDIX WITHIN NORMAL LIMITS.
Negative appendectomy
General
- Common.
- Use for quality control among general surgeons.[citation needed]
Gross
See normal vermiform appendix.
Microscopic
See normal vermiform appendix.
Notes:
- Should be submitted in total.
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VERMIFORM APPENDIX, APPENDECTOMY: - APPENDIX NEGATIVE FOR ACUTE APPENDICITIS AND NEGATIVE FOR ACUTE PERIAPPENDICITIS.
VERMIFORM APPENDIX, APPENDECTOMY: - APPENDIX WITH LYMPHOID HYPERPLASIA AND FOCAL MUCOSAL EROSIONS. - NEGATIVE FOR ACUTE APPENDICITIS. - NEGATIVE FOR ACUTE PERIAPPENDICITIS.
Micro
The sections show appendiceal wall with focal mucosa erosions and several intraluminal neutrophil clusters. Lymphoid hyperplasia is present. Fecal material is present within the lumen of the appendix.
There are no neutrophils within the muscularis propria. There is no serositis. There is no distortion of the crypt architecture. No granulomas are identified. No cryptitis is identified.
Inflammatory pathologies
Acute appendicitis
General
- Bread 'n butter of general surgery.
- Interesting factoid: appendicitis is considered protective against ulcerative colitis.[3][4]
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.
Note:
- Normal diameter of appendix (based on CT): 6.6 +/- 1.5 mm.[2]
- Similar numbers are found in another study.[5]
Microscopic
Features:
- Neutrophils in the muscularis propria - key feature.
- +/- Vascular thrombosis (and necrosis) - known as gangrenous appendicitis.[6]
- +/- Findings suggestive of etiology - usu. absent:
- +/- Fecalith.
- +/- Viral inclusions (extremely rare)
Note:
- Eosinophils are very common.[7]
- Appendices with eosinophils but no apparent neutrophils probably represent the same process.[8]
DDx:
- Mucinous tumour.
- Neuroendocrine tumour.
- Granulomatous appendicitis.
- Crohn's disease of the appendix.
- Approximately of 40% colectomies for CD (that include an appendix) have involvement of the appendix.[9]
Images
Appendicitis - low mag. (WC/Nephron)
Appendicitis - very high mag. (WC/Nephron)
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VERMIFORM APPENDIX, APPENDECTOMY: - ACUTE APPENDICITIS. - ACUTE PERIAPPENDICITIS.
VERMIFORM APPENDIX, APPENDECTOMY: - GANGRENOUS APPENDICITIS. - ACUTE PERIAPPENDICITIS.
Perforated appendicitis
VERMIFORM APPENDIX, APPENDECTOMY: - ACUTE APPENDICITIS WITH PERFORATION AND ACUTE PERIAPPENDICITIS.
This is uncommon to see definitively on histology.
Micro
Gangrenous appendicitis
The sections shows appendiceal wall with marked acute transmural inflammation and necrotic appendiceal wall with large collections of neutrophils. Several medium-sized blood vessels are thrombosed. A thick layer of neutrophils cover the serosal aspect.
Adenovirus appendicitis
General
- Rare type of appendicitis in children.
- Presents as run-of-the-mill acute appendicitis.
- Caused by Adenovirus.
Microscopic
Features:[10]
- Lymphoid hyperplasia - key feature.
- +/-Adenovirus inclusions; "smudge cells".
Notes:
- The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.[10]
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.[11][12]
Microscopic
Features:
- Usu. the appendiceal wall has no inflammation, i.e. there is no appendicitis.[11][12]
- Enterobius vermicularis organisms.
Image
Enterobius - very low mag. (WC/Nephron)
Enterobius - high mag. (WC/Nephron)
Pinworm (WC/Uthman)
.jpg)
Granulomatous appendicitis
General
Most common cause:
- Yersinia appendicitis.[13]
DDx:[14]
- Yersinia appendicitis.[13]
- Yersinia = gram negative rod (red on Gram stain).
- "Safety pin"-like appearance[15] - approximately 0.5 micrometers diameter x 2 micrometers length.
- Other micro-organism (TB, fungus).
- Crohn's disease.
- Sarcoidosis.
- Foreign body reaction.
- Interval (delayed) appendectomy.
- Approximately 60% of delayed appendectomies have granulomas.[16]
Microscopic
Features:
- Granulomas.
- +/-"Safety pin"-like organisms (Yersinia).
Image(s):
Inflammatory bowel disease
Periappendicitis
General
Definition: inflammation of tissues around the (vermiform) appendix.[17]
- 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
| Mucinous tumours of the appendix | |
|---|---|
| External resources | |
| EHVSC | 10183 |
- Benign appendiceal mucocele and appendiceal mucocele redirect here.
General
- There are many classifications and they are controversial.[20]
- The controversy centres on whether to call all mucinous tumours outside of the appendix adenocarcinoma - regardless of whether they have atypia & show invasion.
- Panarelli and Yantiss created a nice summary table - that compare the classifications - see: comparison of classifications (archivesofpathology.org).[20]
- In women - an ovarian primary must be excluded.
- Concurrent bilateral ovarian tumours suggests the tumour originated from the appendix and spread to the ovaries.
- Onlinepathology prefers the classification of Misdraji,[21] as it is the least complicated
Misdraji classification
- 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) as per Misdraji classification:[21]
| 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.
World Health Organization classification
WHO classification:
- Adenoma with low-grade dysplasia.
- Adenoma with high-grade dysplasia.
- Low-grade invasive mucinous adenocarcinoma
- Confined to the appendiceal wall.
- Outside of the appendix.
- High-grade invasive mucinous adenocarcinoma.
Comparison between Misdraji and WHO classification
Adapted from Panarelli and Yantiss:[20]
| Stage | Cytologic dysplasia | Misdraji | World Health Organization |
|---|---|---|---|
| Confined to the mucosa | low-grade | low-grade appendiceal mucinous neoplasm (LAMN) | mucinous adenoma, negative for high-grade dysplasia |
| Confined to the mucosa | high-grade | non-invasive mucinous cystadenocarcinoma of the appendix | mucinous adenoma with high-grade dysplasia |
| At least into the submucosa, confined to the appendix | low-grade | low-grade appendiceal mucinous neoplasm (LAMN) | invasive mucinous adenocarcinoma, low-grade |
| At least into the submucosa, confined to the appendix | high-grade | mucinous adenocarcinoma of the appendix (MACA) | invasive mucinous adenocarcinoma, high-grade |
| Extra-appendiceal spread | low-grade | low-grade appendiceal mucinous neoplasm (LAMN) | invasive mucinous adenocarcinoma, low-grade |
| Extra-appendiceal spread | high-grade | mucinous adenocarcinoma of the appendix (MACA) | invasive mucinous adenocarcinoma, high-grade |
Microscopic
Low-grade appendiceal mucinous neoplasm
- AKA benign mucinous tumour of the appendix.
Microscopic:
- Single layer of epithelium with tufts.
- Vaguely resemble serrations, i.e. the saw-tooth pattern in hyperplastic polyps of the colon.
- Mucin contained (inside appendix only).
- No marked nuclear atypia.
Note:
- May be deceptively bland appearing from a cytologic perspective.
Images:
- LAMN - low mag. (nature.com).[22]
- LAMN - high mag. (nature.com).[22]
- Appendiceal mucocele (pathlabmed.typepad.com).
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.
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LAMN
VERMIFORM APPENDIX, APPENDECTOMY: - LOW-GRADE APPENDICEAL MUCINOUS NEOPLASM. - ACUTE APPENDICITIS. - ACUTE PERIAPPENDICITIS.
VERMIFORM APPENDIX AND CECUM, APPENDECTOMY WITH CECAL CUFF: - LOW-GRADE APPENDICEAL MUCINOUS NEOPLASM (MUCINOUS CYSTADENOMA). - MARGINS NEGATIVE FOR MUCINOUS NEOPLASM. COMMENT: No extra-appendiceal mucin is identified. There is no invasion into the appendiceal wall.
Goblet cell carcinoid
- AKA crypt cell carcinoma.[23]
- AKA neuroendocrine tumour with goblet cell differentiation.
General
- Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.[23]
- Mixed (biphasic) tumour with endocrine and exocrine features.
Microscopic
Features:[24]
- Mixed neuroendocrine-nonneuroendocrine tumour;[25] features of both carcinoid and adenocarcinoma.[24]
- 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
GCC - very high mag. (WC/Nephron)
GCC - very low mag. (WC/Nephron)
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.[24]
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.[26]
Size matters in appendiceal NETs:[27]
- <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.
- ↑ 2.0 2.1 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.
- ↑ 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.
- ↑ Huwart, L.; El Khoury, M.; Lesavre, A.; Phan, C.; Rangheard, AS.; Bessoud, B.; Menu, Y. (Mar 2007). "[What is the thickness of the normal appendix on MDCT?].". J Radiol 88 (3 Pt 1): 385-9. PMID 17457270.
- ↑ URL: http://emedicine.medscape.com/article/363818-overview. Accessed on: 21 June 2010.
- ↑ Aravindan, KP. (Oct 1997). "Eosinophils in acute appendicitis: possible significance.". Indian J Pathol Microbiol 40 (4): 491-8. PMID 9444860.
- ↑ Aravindan, KP.; Vijayaraghavan, D.; Manipadam, MT.. "Acute eosinophilic appendicitis and the significance of eosinophil - Edema lesion.". Indian J Pathol Microbiol 53 (2): 258-61. doi:10.4103/0377-4929.64343. PMID 20551528.
- ↑ Stangl, PC.; Herbst, F.; Birner, P.; Oberhuber, G. (Apr 2002). "Crohn's disease of the appendix.". Virchows Arch 440 (4): 397-403. doi:10.1007/s004280100532. PMID 11956821.
- ↑ 10.0 10.1 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.
- ↑ 11.0 11.1 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
- ↑ 12.0 12.1 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.
- ↑ 13.0 13.1 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.
- ↑ Guo, G.; Greenson, JK. (Aug 2003). "Histopathology of interval (delayed) appendectomy specimens: strong association with granulomatous and xanthogranulomatous appendicitis.". Am J Surg Pathol 27 (8): 1147-51. PMID 12883248.
- ↑ 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.
- ↑ 20.0 20.1 20.2 Panarelli, NC.; Yantiss, RK. (Oct 2011). "Mucinous neoplasms of the appendix and peritoneum.". Arch Pathol Lab Med 135 (10): 1261-8. doi:10.5858/arpa.2011-0034-RA. PMID 21970481.
- ↑ 21.0 21.1 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.
- ↑ 22.0 22.1 Misdraji, J.; Burgart, LJ.; Lauwers, GY. (Dec 2004). "Defective mismatch repair in the pathogenesis of low-grade appendiceal mucinous neoplasms and adenocarcinomas.". Mod Pathol 17 (12): 1447-54. doi:10.1038/modpathol.3800212. PMID 15354187.
- ↑ 23.0 23.1 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.
- ↑ 24.0 24.1 24.2 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.