CT adrenal protocol is preferred modality for characterization. (MRI is backup, not first-line).
If the lesion is determined to be an adenoma, then biochemical evaluation could be considered to determine if it is hyperfunctioning.
Adenoma accounts for the adrenal lesion. While benign, in some patients these can be biochemically/hormonally active. If the patient is symptomatic, laboratory biochemical evaluation might be helpful.