Vermiform appendix
The Vermiform appendix is, usually, just called appendix. 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]
Acute appendicitis
General
- Bread 'n butter of general surgery.
Gross
Features:
- Serosal surface dull.
- May be perforated (best determined on gross).
- +/-Fibrinous exudate.
Definition
- Neutrophils in the muscularis propria.
Microscopic
Features:
- Neutrophils in the muscularis propria.
- +/-Fecalith.
- +/- Vascular thrombosis (and necrosis) - known as gangrenous appendicitis.[2]
DDx
- Mucinous tumour.
- Neuroendocrine tumour.
- Granulomatous appendicitis.
- Crohn's disease of the appendix.
Granulomatous appendicitis
Most common cause:
- Yersinia appendicitis.[3]
DDx:[4]
- Yersinia appendicitis.[3]
- Yersinia = gram negative rod.
- Other micro-organism (TB, fungus).
- Crohn's disease.
- Sarcoidosis.
- Foreign body reaction.
- Interval (delayed) appendectomy.
Microscopic
Features:
- Granulomas.
Tumours of the appendix
Adenocarcinoma
- Like colorectal adenocarcinoma - see colorectal tumours.
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[5]
- benign - low grade mucinous tumour.
- borderline - mucinous tumour of uncertain malignant potential or borderline mucinous tumour.
- malignant - mucinous adenocarcinoma.
Five year survival[5]
| 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
Micro.
- 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
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
- Rare appendiceal tumour that typically has an aggressive course vis-a-vis other appendiceal carcinoid.[6]
- AKA crypt cell carcinoma - probably a better descriptor.[6]
- Mixed (biphasic) tumour with endocrine and exocrine features.
Histology
Features:[7]
- Mixed neuroendocrine-nonneuroendocrine tumour;[8] features of both carcinoid and adenocarcinoma.[7]
- 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.
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.[7]
See also
References
- ↑ Dawkins R. The Greatest Show on Earth: The Evidence for Evolution. ISBN 978-1416594789.
- ↑ URL: http://emedicine.medscape.com/article/363818-overview. Accessed on: 21 June 2010.
- ↑ 3.0 3.1 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
- ↑ 5.0 5.1 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.
- ↑ 6.0 6.1 PMID 18042066.
- ↑ 7.0 7.1 7.2 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.