There are numerous fat-containing adrenal lesions, often benign and non-functional 1.
Benign lesions containing fat:
lipid-rich adrenal adenoma
Malignant lesions may also occasionally contain fat:
adrenocortical carcinoma: rarely contains a fat component
adrenal collision tumor: the most prevalent fat-containing component is an adrenal adenoma
See also
adrenal lesions: for a more general list of adrenal masses