There is a huge, septated mass lesion with predominantly fat density with internal soft tissue components in the retroperitoneal space of the right hemiabdomen (with a slight extension into the left side). The mass lesion is displacing the right kidney superiorly without evidence of hydronephrosis.
Anteriorly, the mass lesion is abutting the interior aspect of the anterior abdominal wall and displacing bowel loops.
Right laterally, the mass lesion is also abutting the abdominal wall. Posteriorly, the mass lesion is abutting the right psoas muscle and right iliac artery without evidence of stenosis or thrombus formation. Medially, the mass lesion is displacing the adjacent bowel loops and mesentery with their contents and abutting the IVC with evidence of luminal narrowing.
The liver is mildly enlarged in size in its normal position and has smooth borders. No discrete focal lesion is appreciated in hepatic parenchyma.
Incidental findings of accessory spleen are seen as well.