CT-Algorithm benign versus malignant adrenal masses.

Mostly an adrenal mass will be found on an enhanced CT that is performed in patients with abdominal complaints or patients that are referred for lung carcinoma staging.
As differentiation between benign and malignant is usually not possible on the initial enhanced CT (at 60sec), ordering the patient back for a dedicated adrenal-CT is the best strategy
( although some prefer MRI).
If on the unenhanced-CT the density is equal to or below 10 HU the lesion is considered to be an adenoma and no further workup is neccessary
If the density is more than 10 HU the wash out should be calculated. 
If the washout is not compatible with an adenoma, a biopsy can be performed if a definitive diagnosis is crucial to the patients management.

Reference