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Surgical Pathology Criteria

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Adenocarcinoma of the Appendix


  • Malignant gland forming appendiceal neoplasm


  • We reserve the term "adenocarcinoma" for neoplasms characterized by invasive glands and or signet ring cells
  • Neoplasms characterized by dissecting mucin (with or without cells), but not invasive glands behave differently and are classified separately as (see Differential Diagnosis at left or follow the links below)

Diagnostic Criteria

  • All types are quite rare
  • All show overtly malignant features
    • Invasion of appendiceal wall by neoplastic epithelium
      • Jagged neoplastic glands beyond the muscularis mucosa
    • Usually exhibits high grade cytologic atypia
      • Frequent mitotic figures
    • Usually exhibits architectural complexity and/or discohesive infiltration
    • Peritoneal implants typically invasive
    • Frequent metastasis to nodes, liver
  • Mucinous adenocarcinoma is similar to that of the colorectum
    • High grade cytology within mucin pools or direct mural invasion by neoplastic glands
    • Must be >50% mucin
    • Very rarely associated with clinical pseudomyxoma peritonei
      • Most peritoneal involvement by carcinoma is better characterized as peritoneal carcinomatosis
  • Intestinal type adenocarcinoma shows features of usual colorectal adenocarcinoma
  • Signet ring carcinoma is similar to that of the colorectum
    • >50% must be made up of signet ring cells
    • Frequent metastasis to ovary
    • Very poor prognosis
    • Distinguish from carcinoma ex-goblet cell carcinoid
      • Lacks any typical goblet cell carcinoid pattern in the primary tumor
  • Appendiceal adenocarcinomas have been reported associated with serrated polyps
    • The nature and extent of association is not clear
  • Virtually all appendiceal adenocarcinomas of all types are microsatellite stable
  • Poor prognosis for all types
    • <10% 10 year survival
Teri A Longacre MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates : 10/7/10, 11/21/11, 2/10/12

Differential Diagnosis

Appendiceal Mucinous Neoplasms
Mucinous Adenoma/Cystadenoma Mucinous Low Risk of Recurrence Mucinous High Risk of Recurrence Mucinous Adenocarcinoma
No extra-appendiceal mucin No epithelium in extra-appendix mucin Epithelium present in extra-appendiceal mucin Epithelium may be present in extra-appendiceal mucin
Non-invasive epithelium may be present in intramural mucin Non-invasive epithelium may be present in intramural mucin Non-invasive epithelium may be present in intra and extramural mucin Invasion by jagged neoplastic glands
Margin of resection must be clear Margin may be involved Margin may be involved Margin may be involved
Benign, no recurrences Very few recur, 0% mortality Frequently recur, 50% 5 year, 20% 10 year survival <10% 10 yr survival

    The distinctions are critical

    Grading / Staging

    • Grading differs somewhat compared to colorectal adenocarcinoma
      • Non-mucinous carcinomas are graded as are colorectal adenocarcinoma NOS
        • Low grade
          • 50-100% gland formation
        • High grade
          • 0-49% gland formation
      • Mucinous carcinomas are definitionally high grade in the appendix
        • Virtually all are microsatellite stable, unlike in the colorectum
      • Signet ring carcinomas are definitionally high grade
    • Staging: TNM from AJCC, similar to colorectal

    Classification / Lists

    Appendiceal Epithelial Neoplasms and Proliferations

    Clinical / Descriptive Terms


    • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
    • Pai RK, Longacre TA. Appendiceal mucinous tumors and pseudomyxoma peritonei: histologic features, diagnostic problems, and proposed classification. Adv Anat Pathol. 2005 Nov;12(6):291-311.
    • Pai RK, Beck AH, Norton JA, Longacre TA. Appendiceal mucinous neoplasms: clinicopathologic study of 116 cases with analysis of factors predicting recurrence. Am J Surg Pathol. 2009 Oct;33(10):1425-39.
    • Yantiss RK, Panczykowski A, Misdraji J, Hahn HP, Odze RD, Rennert H, Chen YT. A comprehensive study of nondysplastic and dysplastic serrated polyps of the vermiform appendix. Am J Surg Pathol. 2007 Nov;31(11):1742-53.
    • Qizilbash AH. Primary adenocarcinoma of the appendix. A clinicopathological study of 11 cases. Arch Pathol. 1975 Oct;99(10):556-62.
    • McCusker ME, Coté TR, Clegg LX, Sobin LH. Primary malignant neoplasms of the appendix: a population-based study from the surveillance, epidemiology and end-results program, 1973-1998. Cancer. 2002 Jun 15;94(12):3307-12.

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