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PubMed Search: Appendiceal mucocele

Matt Andrew M. Paz, D.O.
Aastha Chauhan, M.D.
Page views in 2023 to date: 9,864
Cite this page: Paz MAM, Chauhan A. Mucocele. website. Accessed September 21st, 2023.
Definition / general
  • Appendiceal mucocele is a clinical term referring to a mucus filled, distended appendix
Essential features
  • Asymptomatic distension of the lumen due to the accumulation of mucin
  • Surgical treatment is dependent on dimensions and the histology of the mucocele
  • Mucocele, obstructive mucocele, inflammatory mucocele, simple retention cyst
ICD coding
  • ICD-10: K38.8 - other specified diseases of appendix
  • ICD-11: DB11.6 - mucocele of appendix
  • Mucoceles of the appendix are rare, encountered in 0.2 - 0.3% of appendectomies
  • Usually diagnosed in patients ~50 - 60 years old, with a slight female predominance (Acta Chir Scand 1973;139:392)
  • Rupture of a mucocele can present as acute peritonitis
  • Pathogenesis of appendiceal mucocele is dependent on its etiology
  • Natural history is strongly influenced by anatomic peculiarities of the vermiform appendix that predispose to perforation and subsequent mucinous spillage into the peritoneal cavity
Clinical features
  • Asymptomatic mucoceles are often diagnosed incidentally on imaging or endoscopic procedures
  • Unexpected finding during surgical procedures performed for acute appendicitis or various nonappendiceal pathologies (Am J Case Rep 2014;15:355)
  • Mucoceles have nonspecific laboratory findings
  • Appendiceal mucoceles with a neoplastic etiology may have elevated tumor markers, such as carcinoembryonic antigen (Int J Surg Case Rep 2013;4:886)
Radiology description
Radiology images

Images hosted on other servers:
Hypodense ovoid structure (solid arrow) & curvilinear mural calcification (dashed arrow)

Hypodense ovoid structure

Prognostic factors
  • Prognosis is dependent on the underlying etiology of the lesion
  • Simple mucoceles are benign; they have an excellent prognosis (91 - 100% 5 year survival) and do not recur after standard appendectomy (Dig Dis 1998;16:183)
Case reports
  • Appendectomy for nonneoplastic mucoceles is curative
Gross description
  • Mucus filled, distended appendix
  • Nonneoplastic mucoceles exhibit less dramatic distention, often measuring < 2 cm across the short axis (Cancer 1995;75:757)
Gross images

Images hosted on other servers:
Distended appendix with intact wall

Distended appendix with intact wall

Microscopic (histologic) description
Sample pathology report
  • Appendix, appendectomy:
    • Dilated appendix due to endometriosis and focal scarring
Differential diagnosis
Board review style question #1
A 32 year old woman with history of hematuria coinciding with her menstruation underwent an appendectomy for an incidentally discovered dilated appendix. On gross exam, the appendix appeared dilated. Sectioning revealed a dilated mucin filled lumen with no evidence of neoplasms. What histological findings are supportive of an endometriosis involving an appendix?

  1. Complex villous proliferation of appendiceal epithelium
  2. Flat proliferation of mucinous epithelial cells
  3. Monotonous infiltration of small round cells with speckled nuclei
  4. Unremarkable appendiceal epithelium with focal fibrosis and nests of endometrial stroma
Board review style answer #1
D. Unremarkable appendiceal epithelium with focal fibrosis and nests of endometrial stroma. This patient is presenting with signs of endometriosis. Endometriosis and focal scarring may obstruct the appendix, causing dilation of the lumen and mucus build up. Answer B is incorrect because flat proliferation of mucinous epithelial cells suggests a mucinous neoplasm, likely a low grade appendiceal neoplasm (LAMN). Answer C is incorrect because monotonous infiltration of small round cells with speckled nuclei suggests a neuroendocrine tumor. Answer A is incorrect because complex villous proliferation of appendiceal epithelium refers to a high grade mucinous neoplasm.

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Reference: Mucocele
Board review style question #2
A 54 year old man with a history of acute appendicitis managed conservatively with antibiotics alone presented for an elective appendectomy after his appendix was incidentally found to be dilated in a recent hospital visit. The resected appendix appeared pink-tan with no gross signs of infection. Sectioning revealed focal scarring with no signs of necrosis of neoplasms. Microscopic exam noted focal fibrosis of the mucosa and focal lymphoid aggregates. No other abnormality was identified. What other treatment, if any, is appropriate for this patient?

  1. Intraperitoneal chemotherapy is appropriate
  2. No further treatment is necessary
  3. Right sided hemicolectomy with lymph node dissection
  4. Tumor debulking
Board review style answer #2
B. No further treatment is necessary. This patient presents with an incidentally dilated appendix likely due to scarring from his previous history of acute appendicitis. His clinical picture does not suggest any evidence of an appendiceal neoplasm. Answers A, C and D are incorrect because intraperitoneal chemotherapy, tumor debulking and right sided hemicolectomy with lymph node dissection are not warranted.

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Reference: Mucocele
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