Primary retroperitoneal cysts are rare benign lesions which often present as an incidental radiological finding and also cause abdominal symptoms. A 47-year-old woman was admitted to the surgery unit because of right-sided abdominal pain. Computed tomographic scan investigation confirmed a circumscribed, oval, dishomogeneous mass in the right anterior pararenal space. The final diagnosis was obtained after laparotomy excision and pathological evaluation. Immunohistochemical profile was characterized by positive expression of epithelial cystic cells for CKAE1/AE3, CK7, CK8, and CK18, with EMA sustaining the diagnosis of a benign retroperitoneal cyst of urinary system origin.