Solution: Adrenal myelolipoma is a rare benign tumor composed of hematopoietic elements (myelo) and fat (lipoma). When you encounter a mass this large, the first thing to do is try to determine the origin of the mass. In this case, you can see that it is pushing the liver anteriorly and the kidney inferiorly, but does not seem to be arising from either one. This suggests that it is a retroperitoneal mass arising in the supra-renal space, thus most likely etiologies would be a fatty adrenal mass or a fatty retroperitoneal mass. Calcification is seen in about 20% of these cases. Differential would include a liposarcoma and biopsy would usually be required to differentiate the two (as was done in this case). Although it is uncommon, these tumors can rupture and hemorrhage. They can obviously also cause symptoms related to mass effect, but do not require surgery if the diagnosis is certain.