Patients with pseudomyxoma peritonei associated with disseminated peritoneal adenomucinosis have a significantly more favorable prognosis than patients with peritoneal mucinous carcinomatosis

BACKGROUND. Pseudomyxoma peritonei (PMP) is a poorly understood condition c haracterized by disseminated intraperitoneal mucinous tumors, often with mu cinous ascites. The term PMP has been applied historically as a pathologic diagnostic term to both benign and malignant mucinous neoplasms that produc e abundant extracellular mucin, resulting in a variable and poorly predicta ble prognosis. A recent study reported a pathologic classification that sep arated patients into prognostically distinct groups, but the follow-up was relatively short. METHODS. Long-term follow-up data were analyzed for a previously reported s eries of 109 patients with PMP to examine the prognostic utility of a patho logic classification system that divided patients into three groups: dissem inated peritoneal adenomucinosis (DPAM), peritoneal mucinous carcinomatosis (PMCA), and peritoneal mucinous carcinomatosis with intermediate or discor dant features (PMCA-I/D). Patients whose tumors were classified 25 DPAM (n = 65 patients) had disease that was characterized by histologically bland t o low-grade adenomatous mucinous epithelium associated with abundant extrac ellular mucin and fibrosis, often with an identifiable appendiceal mucinous adenoma that was the source of the peritoneal lesions. Patients whose tumo rs were classified 25 PMCA (n = 30 patients) had disease that was character ized by peritoneal lesions that displayed the cytologic and architectural f eatures of mucinous carcinoma associated with extracellular mucin, often wi th an identifiable invasive mucinous adenocarcinoma of the gastrointestinal tract. Patients whose tumors were classified 25 PMCA-I (n = 11 patients) h ad peritoneal lesions that combined the features of DPAM and PMCA derived f rom well differentiated mucinous adenocarcinomas associated with adenomas. Patients whose tumors were classified 25 PMCA-D (n = 3 patients) had marked ly atypical appendiceal adenomas associated with peritoneal lesions similar to PMCA. RESULTS. Patients with DPAM had 5-year and 10-year survival rates of 75% an d 68%, respectively (mean follow-up, 96 months; median follow-up, 104 month s). Patients with PMCA and PMCA-I/D had a significantly worse prognosis, wi th 5-year and 10-year survival rates, respectively, of 50% and 21% for PMCA -I/D (mean follow-up, 58 months; median follow-up, 51 months) and 14% and 3 % for PMCA (mean follow-up, 27 months; median follow-up, 16 months; P = 0.0 001). CONCLUSIONS. The term PMP should be used only as a clinical descriptor for patients who have the syndrome of mucinous ascites accompanied by a charact eristic distribution of peritoneal mucinous tumors with the pathologic feat ures of DPAM. DPAM should be used as a pathologic diagnostic term for patie nts with the bland peritoneal mucinous tumors associated with ruptured appe ndiceal mucinous adenomas and PMP. These patients should not be diagnosed w ith carcinoma, because they have disease that is distinct pathologically an d prognostically from PMCA. Cancer 2001;92:85-91. (C) 2001 American Cancer Society.