Pseudomyxoma peritonei. Histologic predictors of patient survival.

Pseudomyxoma peritonei is uncommon and the histopathologic predictors of patient survival with this disease have not been investigated extensively. The clinicopathologic features of 35 patients with pseudomyxomatous peritoneal implants (implants that produced extracellular mucin) were compared with a control group of 90 consecutive patients with peritoneal implants without extracellular mucin. The histologic patterns of these nonpseudomyxomatous implants were as follows: glandular, 43%; serous, 21%; signet ring, 20%; solid, 13%; and clear cell, 2%. The pseudomyxomatous implants were more likely to have originated from a mucinous epithelial tumor of the appendix (31% vs 1%). Other primary sites produced pseudomyxomatous and nonpseudomyxomatous implants with similar frequency: colon (26% vs 30%), ovary (23% vs 16%), stomach (11% vs 10%), small intestine (3% vs 1%), urinary bladder (3% vs 1%), endometrium (0% vs 10%), prostate gland (0% vs 6%), and unknown (3% vs 15%). Three-year follow-up was available for 29 of 35 and 71 of 90 patients with and without extracellular mucin in their implants, respectively. The patients with pseudomyxomatous implants survived longer (24% vs 4% survival at 3 years). Three-year follow-up was available for 90 of 110 and 10 of 15 patients with and without invasion in the primary tumor or its peritoneal implants, respectively. The patients without invasive tumors survived longer (80% vs 4% survival at 3 years). Invasion in the primary tumor or its implants, present in 21 of 35 pseudomyxomatous implants, eliminated any improved survival associated with the presence of extracellular mucin. Prolonged survival in pseudomyxoma peritonei was associated with the histologic findings of noninvasive implants arising from mucinous epithelial tumors of low malignant potential histology. In our study, such tumors originated in the appendix (eight cases [23%]) and ovary (five cases [14%]) among the total number of 35 patients.