Figure 25.

Variable appearance of adrenal lesions (white arrowheads) on FDG PET-CT: (a) Axial fused FDG PET-CT. A left adrenal nodule (white arrowhead) is low in attenuation (<10 HU) and is without appreciable metabolic activity, typical findings of lipid-rich adenoma; (b) Axial fused FDG PET-CT. Attenuation is slightly higher (HU 15) and metabolic activity is lower in this adrenal nodule, compared to the metabolic activity of the liver, supporting that this is likely a benign nodule but warrants follow-up for confirmation of stability. Note there is also geographic hepatic steatosis on CT; (c) Axial fused FDG PET-CT. A small adrenal nodule demonstrates metabolic activity 1.8 times that in the liver. This is suspicious for malignancy and further workup is warranted; (d) Axial fused FDG PET-CT. A large intensely hypermetabolic adrenal mass is a metastasis vs. adrenal cortical cancer (in this case it was a metastasis from a primary was non-small cell lung cancer); (e) Coronal fused FDG PET-CT image. Symmetrical hypermetabolism in both adrenal glands without nodularity may represent stressed-induced adrenal activation or adrenal hyperplasia.