Figure 1b. Adrenal adenoma in a 68-year-old man. (a) Unenhanced CT scan shows a smooth, ovoid, well-defined low-attenuation mass (arrow). The CT attenuation value was -5 HU, indicating the presence of intracellular lipid. Korobkin et al (8) demonstrated a cut-off point of 18 HU, below which an adrenal lesion may be designated as a benign adenoma with a specificity of 85% and a sensitivity of 100%. (b) Contrast material-enhanced CT scan shows moderate enhancement of the mass (arrow), which gives the lesion a slightly heterogeneous appearance. (c) Axial in-phase (repetition time msec/echo time msec = 150/4.2) (top) and out-of-phase (150/1.8) (bottom) fast multiplanar spoiled gradient-echo (FMPSPGR) T1-weighted MR images (flip angle = 90°) show the mass with classic signal dropout (arrow), a finding that suggests the presence of intracellular lipid, a characteristic feature of benign adenomas. (d) On an axial fast spin-echo T2-weighted MR image (6,000/105), the adenoma (arrow) is isointense relative to the liver. (e) High-power photomicrograph (original magnification, x400; hematoxylin-eosin [H-E] stain) demonstrates a lipid-rich adrenal adenoma with abundant intracellular fat (arrow).