Pseudomyxoma Peritonei

Definition

• A clinical condition characterized by accumulation of mucin in the abdominal or pelvic cavity

Diagnostic Criteria

• A clinical condition, not a pathologic diagnosis
• Extensive secretion and accumulation of mucin in the peritoneal space
• Usually produces abdominal distension
• Characterized by re-accumulation after debulking
• Ultimately leads to intestinal obstruction
• No metastatic spread to nodes or organ parenchyma other than ovary
• Pleural involvement rare
• Due to communications across the diaphragm
• Approximately 50% 5 year survival with aggressive, repeated debulking
• Disease progresses inexorably to 20% 10 year survival
• Contrasts with very short survival for carcinomatosis
• Histopathologic findings usually correspond to appendiceal mucinous neoplasm with high risk of recurrence
• Paucicellular mucin implants
• Degree of cellularity may be prognostic
• Cytologic atypia should be low grade
• Cytologic atypia does not change with time or recurrences
• High grade cytology is an indication of peritoneal carcinomatosis rather than pseudomyxoma
• Epithelial elements simple or focally proliferative
• Complex, cribriform architecture indicative of carcinomatosis
• Implants should be non-invasive
• Invasion indicates carcinomatosis
• Vast majority of cases of pseudomyxoma peritonei are associated with appendiceal mucinous neoplasms with high risk of recurrence
  • Occasional cases associated with appendiceal mucinous neoplasms with low risk of recurrence
  • Rare reports of association with neoplasms of other sites in most cases probably represent peritoneal carcinomatosis or failure to examine completely the appendix
  • Rarely associated with mucinous neoplasms arising in teratomas

Original posting/updates : 10/7/10

Differential Diagnosis

Pseudomyxoma Peritonei	Peritoneal Carcinomatosis
Primary is mucinous neoplasm of high risk of recurrence of appendix (rarely from teratomas)	Primary is mucinous carcinoma of any GI site
Paucicellular implants	Implants usually cellular
Non-invasive implants	Invasive implants
Low grade cytology	May have high grade cytology
Simple or focally proliferative epithelium	Complex cribriform epithelium
No signet ring cells	May have signet ring component
No nodal or parenchymal metastases (except ovary)	Frequent nodal and parenchymal metastases
Many recurrences, eventual fatalily	Generally rapidly fatal

The distinction is critical

Lists

Appendiceal Epithelial Neoplasms and Proliferations

• Adenocarcinoma
• Carcinoid / well differentiated neuroendocrine neoplasm
• Carcinoma ex-goblet cell carcinoid
• Goblet cell carcinoid
• Hyperplastic polyp / mucosal hyperplasia
• Mucinous adenoma / cystadenoma
• Mucinous neoplasm with high risk of recurrence
• Mucinous neoplasm with low risk of recurrrence
• Sessile serrated polyp / adenoma
• Traditional serrated adenoma

Clinical / Descriptive Terms

• Mucocele
• Pseudomyxoma peritonei

Bibliography

• 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.
• 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.
• McKenney JK, Soslow RA, Longacre TA. Ovarian mature teratomas with mucinous epithelial neoplasms: morphologic heterogeneity and association with pseudomyxoma peritonei. Am J Surg Pathol. 2008 May;32(5):645-55.