Cystic mesothelioma of the peritoneum: a report of five cases and review of the literature.

Five cases of the recently characterized cystic mesothelioma of the peritoneum are presented. The patients, all women, ranged in age from 23-50, and were seen with large, solitary or multiple, multicystic masses involving the abdominal and pelvic peritoneum. Histologically, they consisted of interconnecting cystic cavities lined by a single layer of flattened to cuboidal cells with variable nuclear atypia. These cells in one case showed ultrastructural features consistent with mesothelial origin. In follow-up periods ranging from 1-13 years, two patients have had recurrence of disease, but all patients are still alive. When these cases are combined with the ten previously reported, the recurrence rate in patients followed for two years or more is 50% (four of eight). This lesion may represent a clinically "borderline" variant between the better known benign (adenomatoid tumor) and malignant mesotheliomas of the peritoneum.