Extracellular contrast (Gadovist) was utilized.
The hypoattenuating retroperitoneal mass on CT corresponds with a large retroperitoneal mass of heterogeneous T2 signal and low T1 signal, measuring 15 x 10 x 7.6 cm. The mass demonstrates gradual heterogeneous enhancement, a mixture of T2 shine through and mild diffusion restriction, and no frank fat signal. The mass displaces the adjacent viscera (including the stomach, pancreas, and left lobe of the liver) as well as the superior mesenteric vein, confluence of the SMV and splenic vein, and the portal vein; the portosystemic circulation remains patent.
Normal background liver. No liver metastases.
Conventional arterial anatomy (narrowed celiac axis with a median arcuate compression type picture).
Thin-walled gallbladder with small volume biliary sludge, without biliary dilatation.
Normal pancreas, adrenals, kidneys and spleen. No free abdominal fluid.
Impression:
Unusual large retroperitoneal mass with local mass effect but no local invasion. Felt unlikely to be of liver or pancreatic origin. Exact etiology unclear; a tumor of neural origin is likely the top differential, but a low-grade sarcoma is not excluded.
The mass abuts the stomach and duodenum and EUS-guided biopsy is the best option for tissue.