[Histologic classification and prognostic implication of pseudomyxoma peritonei].

Objective: To clarify the various diagnostic connotations of pseudomyxoma peritonei (PMP) and to study their prognostic implications.
Methods: Clinicopathologic features and follow-up data of 40 patients with PMP diagnosed in The General Hospital of PLA were retrospectively reviewed. The cases were histologically classified into 3 subcategories: disseminated peritoneal adenomucinosis (DPAM), peritoneal mucinous carcinomatosis (PMCA), and PMCA with intermediate or discordant features (PMCA-I/D). The survival rate was calculated using Kaplan-Meier method and the difference was statistically analyzed.
Results: Twelve of the 40 patients died on follow up. The duration of survival ranged from 2 to 348 months (medium = 37.5 months). In general, the 3-year, 5-year and 10-year survival rates were 79.0%, 69.4% and 53.0%, respectively. The mean age of the patients at the time of diagnosis was 50.3 years (age range = 22 to 76 years). The male-to-female ratio was 1:1. The age and sex of patients, frequency of operation and presence of ovarian involvement did not correlate with duration of survival. On the other hand, the presence of appendiceal tumor, parenchymal invasion of abdominal viscera, cellularity, architecture, nuclear atypia and mitotic activity of the peritoneal lesion significantly correlated with survival. There was also significant difference in survival between DPAM, PMCA-I/D and PMCA subcategories (P = 0.018). The difference in survival rate between PMCA-I/D and PMCA subgroups however was not statistically significant (P = 0.096). The outcome of DPAM was significantly better when compared with the combined group of PMCA-I/D and PMCA (P = 0.006).
Conclusions: In general, the 10-year survival rate of PMP was low, despite the relatively benign-looking or low-grade pathologic appearance. Peritoneal lesions with higher cellularity, conspicuous nuclear atypia and higher mitotic activity are associated with a lower survival rate. The prognosis was even worse in the presence of appendiceal carcinoma or parenchymal invasion of abdominal viscera. It is thus advisable to subclassify PMP into DPAM, PMCA and PMCA-I/D, due to the difference in prognostic implication.