Overall Survival is More Closely Associated with Peritoneal than Primary Appendiceal Pathological Grade in Pseudomyxoma Peritonei with Discordant Pathology

Ann Surg Oncol. 2022 Apr;29(4):2607-2613. doi: 10.1245/s10434-021-10994-z. Epub 2021 Nov 3.


Background: The WHO classification of mucinous appendix neoplasms and pseudomyxoma peritonei (PMP) describes low- and high-grade histology and is of prognostic importance. The metastatic peritoneal disease grade can occasionally be different from the primary appendix tumor. This analysis aimed to report outcomes from a high-volume center in patients with pathological discordance.

Methods: This was a retrospective analysis of prospective data of patients treated by cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for PMP at a single institution between January 2016 and December 2020. Reporting was by pathologists with a special interest in peritoneal malignancy. Discordant pathology was classified as a low-grade primary appendix tumor with high-grade peritoneal disease, or a high-grade primary appendix tumor with low-grade peritoneal disease. Outcomes analyzed were overall and recurrence-free survival, and Kaplan-Meier survival curves and the log-rank test were used to analyze the outcomes.

Results: Between 2016 and 2020, 830 patients underwent CRS and HIPEC for PMP, of whom 37 (4.4%) had discordant pathology. The primary appendix tumors were low-grade in 23 patients and high-grade in 14 patients. The median Peritoneal Cancer Index (PCI) was significantly higher in patients with a low-grade primary tumor (31 vs. 16; p = 0.001), while complete cytoreduction (CC0/1) was achieved in 31/37 (83.8%) patients. The median follow-up was 19 months. Overall survival was worse in those with high-grade peritoneal disease (p = 0.029), whereas recurrence-free survival was similar in both groups (p = 0.075).

Conclusion: In PMP with pathological discordance, the peritoneal disease grade influences prognosis and survival.

MeSH terms

  • Appendiceal Neoplasms* / pathology
  • Appendiceal Neoplasms* / therapy
  • Appendix* / pathology
  • Combined Modality Therapy
  • Cytoreduction Surgical Procedures
  • Humans
  • Hyperthermia, Induced*
  • Prospective Studies
  • Pseudomyxoma Peritonei* / pathology
  • Pseudomyxoma Peritonei* / therapy
  • Retrospective Studies
  • Survival Rate