Imaging features of uncommon adrenal masses with histopathologic correlation.

Uncommon adrenal masses include cystic lesions (hydatid cyst, endothelial cyst), solid lesions (hemangioma, ganglioneuroma, angiosarcoma, primary malignant melanoma), and solid fatty lesions (myelolipoma, collision tumor). Most of these lesions do not have specific imaging features. The liquid content of adrenal cysts is clearly demonstrated on ultrasonographic scans, computed tomographic scans, and magnetic resonance images. Nevertheless, the histologic type cannot be predicted except at some stages of hydatid disease in which pathognomonic features are present. The most typical imaging features of hemangioma are phleboliths and enhancement of peripheral vascular lakes. Ganglioneuroma has nonspecific radiologic features, but this diagnosis should be considered in cases with early enhancement of fine septa and progressive filling. The radiologic features of angiosarcoma and primary malignant melanoma are nonspecific. A macroscopic lipid content within an adrenal mass is theoretically characteristic of myelolipoma. This diagnosis should be made with caution, especially when the lipid content is not predominant, because of the possible association with an adenoma.