There is a large well-defined retroperitoneal lesion measuring 14.1 cm in maximum dimension. There is internal complexity and the impression of enhancement on the portal venous phase, though this is not certain in the absence of a pre-contrast series. No avid arterial enhancement.
The lesion lies above and wraps around the hepatic artery though there is no associated vessel stricturing. The mass runs alongside the superior mesenteric vein/splenic confluence and portal vein which are displaced but not stenosed.
The pancreas is in contact with the lesion but it is unclear whether this is arising from the pancreas. The pancreas appears normal with no features to suggest acute or chronic pancreatitis.
Normal biliary tree.
Arcuate ligament associated narrowing of the celiac axis. Otherwise patent non- stenosed abdominal vasculature.
Rest of the solid organs are unremarkable. Bowels are unremarkable. No free gas seen.
Unremarkable lung bases and bone review
Comment: Large well-defined retroperitoneal lesion with internal complexity but no overtly malignant features. This may represent a benign lymphatic malformation but a malignant retroperitoneal lesion such as sarcoma is a differential. The increasing amylase suggests mass effect on the pancreas which is concerning for growth.