Abstract
Primary retroperitoneal cystadenomas are extremely rare. This is the first report in literature to describe a primary retroperitoneal cystadenoma with a sarcoma-like mural nodule. A 45-year-old woman complained of a left-sided abdominal mass. A computed tomography scan revealed a cystic mass with a mural nodule, which seemed to originate from the tail of the pancreas. At laparotomy the cyst was not adhered to the pancreas but localized retroperitoneally. Histologic examination showed a mucinous cystadenoma with only foci of borderline malignancy with a mural "sarcoma-like" nodule. In view of the surgical and histopathological findings, the mucinous cystadenoma was regarded as primary retroperitoneal. This case demonstrates that in the era of radiological preoperative refinement, pathological diagnosis remains of utmost importance, especially for rare cases.