Vermiform appendix

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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:

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VERMIFORM APPENDIX WITHIN NORMAL LIMITS.

Negative appendectomy

General

Gross

See normal vermiform appendix.

Microscopic

See normal vermiform appendix.

Notes:

DDx:

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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

Main article: Acute appendicitis

Adenovirus appendicitis

General

  • Rare type of appendicitis in children.
  • Presents as run-of-the-mill acute appendicitis.
  • Caused by Adenovirus.

Microscopic

Features:[3]

  • Lymphoid hyperplasia - key feature.
  • +/-Adenovirus inclusions; "smudge cells".

Notes:

  • The classic finding of appendicitis (neutrophils infiltrating into the muscularis propria) may be absent.[3]

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.[4][5]

Microscopic

Features:

Image

  • Enterobius - very low mag. (WC/Nephron)

  • Enterobius - high mag. (WC/Nephron)

  • Pinworm (WC/Uthman)

Granulomatous appendicitis

General

Most common cause:

  • Yersinia appendicitis.[6]

DDx:[7]

  • Yersinia appendicitis.[6]
    • Yersinia = gram negative rod (red on Gram stain).
    • "Safety pin"-like appearance[8] - 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.[9]

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.[10]

  • 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.[11][12]

Microscopic

Features:

  • Acute inflammation of the serosa.

Tumours of the appendix

Adenocarcinoma

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.[13]
    • 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).[13]
  • 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,[14] 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:[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.

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:[13]

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:

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

General

  • Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoids.[16]
  • Mixed (biphasic) tumour with endocrine and exocrine features.

Microscopic

Features:[17]

  • Mixed neuroendocrine-nonneuroendocrine tumour;[18] features of both carcinoid and adenocarcinoma.[17]
    • 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.[17]

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.[19]

Size matters in appendiceal NETs:[20]

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

Gross

  • Classically found in the tip of the appendix.

Image:

  • Appendiceal neuroendocrine tumour. (WC)

Microscopic

Features:

IHC

Features:

  • Chromogranin A -ve/+ve.
  • Synaptophysin +ve.

See: neuroendocrine tumours.

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 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.
  4. ↑ 4.0 4.1 Wiebe, BM. (Mar 1991). "Appendicitis and Enterobius vermicularis.". Scand J Gastroenterol 26 (3): 336-8. PMID 1853157.
  5. ↑ 5.0 5.1 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.
  6. ↑ 6.0 6.1 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.
  7. ↑ http://granuloma.homestead.com/appendicitis.html
  8. ↑ URL: http://www.cdc.gov/ncidod/dvbid/plague/p1.htm. Accessed on: 30 June 2011.
  9. ↑ 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.
  10. ↑ URL: http://www.medilexicon.com/medicaldictionary.php?t=66889. Accessed on: 1 June 2011.
  11. ↑ 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.
  12. ↑ O'Neil, MB.; Moore, DB. (Sep 1977). "Periappendicitis: Clinical reality or pathologic curiosity?". Am J Surg 134 (3): 356-7. PMID 900337.
  13. ↑ 13.0 13.1 13.2 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.
  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 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.
  16. ↑ 16.0 16.1 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.
  17. ↑ 17.0 17.1 17.2 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
  18. ↑ 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.
  19. ↑ 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.
  20. ↑ 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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