[A case of CA19-9-positive retroperitoneal mucinous adenocarcinoma].

We report a case of retroperitoneal mucinous adenocarcinoma in a 44-year-old woman, who was admitted to our hospital complaining of low grade fever. Computed tomography and magnetic resonance imaging demonstrated a cystic tumor located at the lower pole of left kidney with irregular wall, which was enhanced by contrast medium. Open surgery was performed. Macroscopically, the tumor was clearly separated from the left kidney, and diagnosed as retroperitoneal in origin. Histopathological diagnosis was mucinous adenocarcinoma of retroperitoneum and immunohistochemical staining was positive for CA19-9, but not for CA125. The patient had no recurrence for 19 months post-operatively.