Mucinous tumours of the appendix

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Mucinous tumours of the appendix are uncommon tumours of the vermiform appendix that can have a benign or malignant behaviour.

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.[1]
    • 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).[1]
  • In women - an ovarian primary must be excluded.
    • Concurrent bilateral ovarian tumours suggests the tumour originated from the appendix and spread to the ovaries.
  • The classification by Misdraji et al.[2] is a good starting point if one is unfamilar with the topic, 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:[2]

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:[1]

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

www:

  • Mucinous cystadenoma - low mag. (WC)

  • Mucinous cystadenoma - intermed. mag. (WC)

  • Mucinous cystadenoma - high mag. (WC)

  • Mucinous cystadenoma - high mag. (WC)

  • Mucinous cystadenoma - very high mag. (WC)

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.

Sign out

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.

WHO

APPENDIX, APPENDECTOMY:
- APPENDICEAL MUCINOUS CYSTADENOMA WITH EXTENSIVE CALCIFICATION.
-- NEGATIVE FOR HIGH-GRADE DYSPLASIA.
- NEGATIVE FOR MALIGNANCY.

See also

References

  1. ↑ 1.0 1.1 1.2 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.
  2. ↑ 2.0 2.1 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.
  3. ↑ 3.0 3.1 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.
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