Mucinous cystadenocarcinoma of the retroperitoneum: report of a case.

Retroperitoneal mucinous cystadenocarcinomas are extremely rare. A 40-year-old Japanese woman was found to have a retroperitoneal mucinous cystadenocarcinoma of ovarian type. Both ovaries were normal. Concentrations of carcinoembryonic antigen and carbohydrate antigen 19-9 in the cyst fluid were extremely high (810,000 ng/ml and 8,082,000 IU/l, respectively). The tumor varied from benign to borderline and malignant in microscopic appearance, and the lesion was composed of mesothelium-like cells. The histologic and immunohistochemical findings suggested that the tumor developed from mucinous metaplasia of the coelomic mesothelium.