Benign retroperitoneal cyst of Mullerian type.

Retroperitoneal cysts are rare, usually asymptomatic, lesions. We present the case of a 42-year-old woman with an asymptomatic abdominal mass. The mass excised at our district hospital was found in the retroperitoneum. Histologically, the cyst was lined with benign Mullerian-type epithelium. The classification, aetiology and clinical manifestations of retroperitoneal cysts are discussed. Retroperitoneal cysts present as an acute abdomen in only a minority of cases. Ultrasound is the most reliable test for their detection, usually followed by computed tomography and/or an upper gastrointestinal series. Optimally, these cysts should be completely excised.