The diagnosis of<unk>  cannot be made on the basis of the results of laboratory studies. CT is the best diagnostic modality: a confluent mass surrounding the aorta and common iliac arteries can be seen. On MRI, it has low T1 signal intensity and variable T2 signal. Malignant<unk>  usually give uneven MRI signals, bulky, extend above the origins of renal arteries, or displace aorta anteriorly. Besides, malignant<unk>  less frequently displaces ureter medially when compared to other<unk> . On fludeoxyglucose (18F) (FDG) positron emission tomography (PET) scan, it will show accumulation of FDG in the affected area. Although biopsy is not usually recommended, it is appropriate when malignancy or infection is suspected. Biopsy should also be done if the location of<unk>  is atypical or if there is an inadequate response to initial treatment.
Retroperitoneal fibrosis
Perineal tear
Cervical effacement
Perineal hernia
Encapsulating peritoneal sclerosis
Accessory pancreas
Ileosigmoid knot
Cyst