Proposed classification of pseudomyxoma peritonei: influence of signet ring cells on survival

Abstract

The nomenclature and classification of pseudomyxoma peritonei (PMP) is confusing and controversial. Numerous classification systems have been proposed, none of which are easily reproducible or a useful guide for treatment. Patients with PMP of appendiceal origin were identified from our institution's database. Kaplan-Meier analyses were performed based on a proposed new PMP classification, a three-tiered grading system designated PMP1, PMP2, and PMP3. These results were compared with the established schemes by Ronnett and Bradley et al. There were 211 patients included in the analysis with a mean age of 51 ± 12 years at diagnosis. For PMP1, 86 patients (40.8%) included cases with abundant extracellular mucin and columnar nonstratified epithelium without dysplasia or atypia. For PMP3, 50 patients (23.7%) consisted of PMP with any percentage of signet ring cells (SRCs), For PMP2, 75 patients (35.5%) included all other patients. The mean age (± standard deviation) for PMP 1, 2, and 3 were 51 ± 12, 51 ± 12, and 51 ± 10 years, respectively (P = 0.90). The three groups had similar sex distribution (P = 0.24) and resection status (P = 0.47). Kaplan-Meier analyses showed median survivals of 120, 88, and 40 months and 5-year survival rates of 85.7, 63.05, and 32.2 per cent (P < 0.0001) for PMP 1, 2, and 3, respectively. Three distinct categories, PMP1, 2, and 3, were identified, which provide better stratification in terms of overall survival and represent differences in tumor biology that may impact treatment recommendations.