Papillary serous carcinoma of the peritoneum in women. A clinicopathologic and immunohistochemical study.

Background: Papillary serous carcinoma of the peritoneum (PSCP) is a primary peritoneal tumor in women that histologically resembles papillary serous carcinoma of the ovary (PSCO). Recognition of PSCP as an entity is controversial, as is the histogenesis, histopathologic differential diagnosis, and treatment.
Methods: Ten cases of PSCP retrieved from the pathology files of 4 hospitals in Kyoto and Nara, Japan, were studied clinicopathologically and immunohistochemically.
Results: Patient ages at presentation ranged from 40 to 74 years (median, 56 years). All patients were Asian (Japanese). None of the patients had a history of asbestos exposure. Most of the patients had abdominal swelling, ascites with positive cytology, and elevated serum CA125. At surgery, omental tumors with dissemination to the abdominal and pelvic peritoneum were found in all patients. The histology was similar to that of Grade 2 to 3 PSCO. Immunohistochemical studies using a panel of monoclonal antibodies against carbohydrates showed that Lewis Y is a good marker, in addition to S-100, placental alkaline phosphatase, CA125, and CD15 for separating PSCP from malignant mesothelioma (MM). With cytoreductive surgery and cisplatin-based combination chemotherapy and in some cases adoptive immunotherapy and radiation, a median survival of 27 months and a 5-year survival rate of 27% were attained. One patient with Grade 3 tumor has survived for more than 6 years after surgery.
Conclusions: (1) Papillary serous carcinoma of the peritoneum is a definite clinicopathologic entity; (2) immunohistochemistry is a useful tool for distinguishing PSCP from MM; (3) cytoreductive surgery and cisplatin-based combination chemotherapy with other adjunct therapies such as immunotherapy and radiation may improve patient survival in PSCP.