Papillary serous carcinoma of peritoneum: case study and review of the literature on the differential diagnosis of malignant peritoneal tumors.

The distinction between malignant mesothelioma and other malignant neoplasms diffusely involving the peritoneum is important for proper patient treatment. The extra-ovarian peritoneal serous papillary carcinoma is a rare, primary, multicentric peritoneal tumor that is morphologically identical to ovarian serous carcinoma of equivalent grade, but can spare or minimally involve the ovaries. We report such a tumor in a 65-year-old female who had abdominal swelling, ascites with positive cytology and a high grade of nuclear atypia in malignant cells as well as elevated serum CA125. Exploratory laparotomy findings of intrabdominal carcinomatosis were not accompanied by any evident primary site; so the diagnosis of a primary papillary serous neoplasia of the peritoneum was strongly considered. Since the amount of residual disease may be an important prognostic determining factor in primary papillary serous carcinoma of the peritoneum, the patient was debulked to no macroscopic disease and was then given platin-based chemotherapy. The tumor's differential diagnosis from malignant mesothelioma was based, apart from morphologic criteria, on the tumor's immunoreactivity to MOC-31, Ber-EP4 and TAG-72, as well as on the lack of immunostaining for keratin 5/6 and calretinin. Differential diagnosis from ovarian cancer was possible only after the pathological examination of the surgically resected ovaries; the tumor showed minimal superficial invasion of the ovarian cortex.