A unique benign mucinous cystadenoma of the retroperitoneum: a case report and review of the literature.

Primary retroperitoneal mucinous cysts are rare. Most often malignant, lesions present on a spectrum, fitting the histopathological categories of benign, borderline and malignant. The rarest form is the benign mucinous cystadenoma adenocarcinoma, of which only 20 cases have been reported. We present here the curious case of a 37-year-old woman with two large, fast growing, cystic, benign, primary retroperitoneal mucinous cystadenomas treated definitively by local resection.