First, a subset of pheochromocytomas may demonstrate greater than 60% washout on adrenal protocol CT and could potentially be misdiagnosed as lipid-poor adenomas. It is for this reason that bio- chemical evaluation is recommended by the American Association of Clinical Endocrinologists and the American Asso- ciation of Endocrine Surgeons even for masses with benign imaging features.

“Myelolipoma is an uncommon benign tumor composed of mature adipose cells and hematopoietic tissue. The prevalence in autopsy series is between 0.08% and 0.2% . Typically, myelolipoma arises in the adrenal gland. Extra-adrenal myelolipoma is rare and is found most commonly in the presacral and other retroperitoneal areas . Usually asymptomatic and discovered incidentally at cross-sectional imaging, myelolipoma occasionally causes discomfort due to compression or hemorrhage.”
CT and MR Imaging of Extrahepatic Fatty Masses of the Abdomen and Pelvis: Techniques, Diagnosis, Differential Diagnosis, and Pitfalls
Pereira JM et al.
RadioGraphics January 2005 vol. 25 no. 1 69-85