Features and Treatment of Peritoneal Metastases from Solid Pseudopapillary Neoplasms of the Pancreas.

Background: Solid pseudopapillary neoplasms (SPNs) of the pancreas may present widespread peritoneal metastases, but the treatment of this malignancy has not been well described and requires further investigation. Material/Methods: Four cases of SPN with significant peritoneal metastases in our department were operated and retrospectively summarized after long-term follow-up. Eight more cases of peritoneal metastatic SPN from the PubMed database were also included in the analysis. Results: Peritoneal metastases of SPNs have different gross features. The benign nodules were tenacious and well encapsulated, while the malignant nodules were soft and prone to slow bleeding. However, neither of these nodules invaded the small intestines or mesentery. Of the 12 disseminated cases, 7 had history of primary tumor rupture, whereas the others had tumors malignant in nature. A total of 14 surgical events were documented, including 3 complete cytoreductive surgeries (CCRS), 9 cytoreductive surgeries (CRS), and 2 debulking surgeries. After follow-up ranging from 0.3 to 6.1 years, the results of the Fisher's exact test showed no difference between CCRS and CRS in treating either low-grade or high-grade malignant SPNs (P=0.257 and P=0.203, respectively). For all cases of SPN with peritoneal metastases, the CCRS procedure could significantly improve tumor-free survival (TFS) compared to the CRS procedure (P=0.046). Conclusions: SPN rupture could cause significant peritoneal metastases, and either disruption or biopsy of these lesions should be avoided. Peritoneal metastases from SPNs vary both in gross features and biological mechanisms. CCRS may offer optimal therapeutic outcomes and longer TFS for individuals with significant peritoneal metastases of SPNs.