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Surgical Pathology Criteria

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Appendiceal Mucinous Neoplasm with High Risk of Recurrence


  • Neoplasm of the appendix with features of mucinous adenoma but with evidence of epithelial spread beyond the muscularis propria

Alternate/Historical Names

  • Borderline mucinous tumor
  • Disseminated peritoneal adenomucinosis
  • Low grade mucinous neoplasm (WHO preferred term, includes low and high risk of recurrence neoplasms, see Controversy)
  • Mucinous carcinoma (see Controversy)
  • Mucinous neoplasm of low malignant potential
  • (Note that ovarian involvement has by some been taken to represent a primary ovarian carcinoma, see Controversy)

Diagnostic Criteria

  • Epithelial lesion oexhibiting features of mucinous adenoma (see detailed adenoma criteria)
    • Simple mucinous columnar epithelium
    • Low grade dysplasia
    • Sessile, usually circumferential, lining of appendiceal luminal surface
  • Extra-appendiceal mucinous implants containing epithelium
    • Frequent mucin dissection of the wall
      • Neoplastic epithelium may be present in intramural mucin
    • Commonly associated with luminal dilation
  • Implants largely intraperitoneal
    • Implants frequently paucicellular
    • Frequently involves surface of liver and spleen
    • Frequently involves ovary
      • May produce mucinous cysts that have the appearance of primaries (see Controversy)
    • May involve lining of fallopian tubes
  • No metastases to nodes or parenchyma of organs other than ovary
  • Mucinous neoplasm with high risk of recurrence is the most frequent cause of pseudomyxoma peritonei
    • Extensive mucin secretion producing abdominal distension
  • Specimen may need to be entirely submitted to make this diagnosis
  • Occasional cases may have discrepant findings of invasive carcinoma in implants but typical low grade neoplasm in the appendix
    • Clinical significance is unclear
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, 2/10/12


  • Low grade mucinous neoplasm - WHO proposed alternate name
    • Term proposed to encompass mucinous neoplasms with low and high risks of recurrence
    • Proposed because all are composed of histologically identical adenomatous appearing epithelium
    • We prefer not to combine these processes as their clinical behavior is quite different
      • Mucinous neoplasm with low risk of recurrence has very low morbidity and mortality
      • Mucinous neoplasm with high risk of recurrence has considerable morbidity and mortality
    • Furthermore, the term could be confused with low grade adenocarcinoma
      • This is an ordinary colonic type adenocarcinoma, which has a more aggressive course
  • Mucinous carcinoma - proposed alternate name
    • Term proposed as alternate to mucinous neoplasm with high risk of recurrence
    • We prefer to reserve this term for neoplasms capable of metastasis to organs such as lymph node, lung and liver (parenchyma)
    • Mucinous carcinoma of all GI sites behaves aggressively, with metastases
  • Does ovarian involvement represent spread from the appendix?
    • Alternative possibilities include
      • Simultaneous primaries, perhaps due to a field defect
      • Ovarian primary with spread to appendix in some cases
      • No clinical importance to the distinction as long as:
        • Frequent association of appendiceal and ovarian disease is recognized
        • Frequent association with pseudomyxoma peritonei is recognized

Supplemental studies


CDX2 100%
CK7 Variable, frequently positive
CK20 100%
MUC2 100%
MUC5AC 100%


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


    Appendiceal Mucinous Neoplasm with High Risk of Recurrence Appendiceal Endometriosis with Mucin Extravasation
    Lacks endometrioid epithelium Associated with endometrioid epithelium
    Lacks endometrial stroma Associated with endometrial stroma


    • Frequent cause of pseudomyxoma peritonei
      • Abundant mucin secretion by implants
        • Causes abdominal distention
        • Long clinical course
        • Multiple recurrences
      • Surgical debulking is worthwhile, both at presentation and for recurrences
      • 50% 5 year, 20% 10 year survival
        • Death usually caused by intestinal obstruction after multiple recurrences
    • Some question as to whether or not right colectomy is indicated
    • Frequent involvement of ovary
      • In all cases of appendiceal mucinous neoplasms, the ovaries should be examined
      • In all cases of ovarian mucinous neoplasms, the appendix should be examined (or removed)
      • In all cases of pseudomyxoma peritonei the appendix and the ovaries should be examined


    Appendiceal Epithelial Neoplasms and Proliferations

    Clinical / Descriptive Terms


    • 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.
    • Bosman FT, Carneiro F, Hruban RH, Thiese ND (Eds). WHO Classifiication of Tumors of the Digestive System, IARC, Lyon 2010
    • Seidman JD, Elsayed AM, Sobin LH, Tavassoli FA. Association of mucinous tumors of the ovary and appendix. A clinicopathologic study of 25 cases. Am J Surg Pathol. 1993 Jan;17(1):22-34.
    • Young RH, Gilks CB, Scully RE. Mucinous tumors of the appendix associated with mucinous tumors of the ovary and pseudomyxoma peritonei. A clinicopathological analysis of 22 cases supporting an origin in the appendix. Am J Surg Pathol. 1991 May;15(5):415-29.
    • Misdraji J, Yantiss RK, Graeme-Cook FM, Balis UJ, Young RH. Appendiceal mucinous neoplasms: a clinicopathologic analysis of 107 cases. Am J Surg Pathol. 2003 Aug;27(8):1089-103.
    • Sumithran E, Susil BJ. Concomitant mucinous tumors of appendix and ovary. Result of a neoplastic field change? Cancer. 1992 Dec 15;70(12):2980-3.
    • Nonaka D, Kusamura S, Baratti D, Casali P, Younan R, Deraco M. CDX-2 expression in pseudomyxoma peritonei: a clinicopathological study of 42 cases. Histopathology. 2006 Oct;49(4):381-7.
    • Bradley RF, Stewart JH 4th, Russell GB, Levine EA, Geisinger KR. Pseudomyxoma peritonei of appendiceal origin: a clinicopathologic analysis of 101 patients uniformly treated at a single institution, with literature review. Am J Surg Pathol. 2006 May;30(5):551-9.
    • Ronnett BM, Zahn CM, Kurman RJ, Kass ME, Sugarbaker PH, Shmookler BM. Disseminated peritoneal adenomucinosis and peritoneal mucinous carcinomatosis. A clinicopathologic analysis of 109 cases with emphasis on distinguishing pathologic features, site of origin, prognosis, and relationship to "pseudomyxoma peritonei". Am J Surg Pathol. 1995 Dec;19(12):1390-408.
    • Ronnett BM, Yan H, Kurman RJ, Shmookler BM, Wu L, Sugarbaker PH. Patients with pseudomyxoma peritonei associated with disseminated peritoneal adenomucinosis have a significantly more favorable prognosis than patients with peritoneal mucinous carcinomatosis. Cancer. 2001 Jul 1;92(1):85-91.
    • Yantiss RK, Shia J, Klimstra DS, Hahn HP, Odze RD, Misdraji J. Prognostic significance of localized extra-appendiceal mucin deposition in appendiceal mucinous neoplasms. Am J Surg Pathol. 2009 Feb;33(2):248-55

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