Abstract
Background: Pseudomyxoma peritonei (PMP) is a rare condition characterized by gelatinous ascites. Although the histologic attributes of PMP have been well studied, the cytologic features remain ill defined. Methods: We reviewed the peritoneal washings (PW) in 67 patients with PMP to identify cytomorphologic features useful in classifying cases as either disseminated peritoneal adenomucinosis (DPAM) or peritoneal mucinous carcinomatosis (PMCA). Histologic specimens were correlated with the cytologic diagnoses. Correlation between cytologic diagnosis and patient outcome was investigated. Results: Neoplastic epithelial cells were identified in 63 of 67 PW (94%). Concordance with the histologic diagnosis was obtained in 61 of 63 cases. Of these 36.5% were cytologically classified as DPAM with primary appendiceal neoplasms in 19 cases. Thirty-four of 63 cases (53.9%) were cytologically diagnosed as PMCA based on PW cytology. Most were of appendiceal or colonic origin. Four cases displayed cytologic features of both DPAM and PMCA. Two discordant cases each with a cytologic diagnosis of PMCA had an appendiceal adenoma. Acellular mucin alone was identified in the PW in four cases. Analysis of follow-up data revealed that cases diagnosed as DPAM had a better prognosis than those diagnosed as PMCA. Conclusions: Cytomorphologic features of epithelial cells in PW material can accurately categorize cases of PMP as either DPAM or PMCA. Furthermore, this categorization appears to have important prognostic implications.