Adrenal Myelolipoma

Adrenal myelolipoma is a rare benign tumor composed of mature fat and hematopoietic tissues. CT shows a heterogeneously fatty mass with Hounsfield units between -90 and -30. Punctate calcifications may be present.

Ultrasound shows a hyperechoic mass with areas of decreased echogenicity corresponding to the myeloid component.

MRI shows fat signal on T1- and T2-weighted images with areas of intermediate signal intensity (similar to spleen) corresponding to the myeloid components. Macroscopic fat is typical of myelolipoma, but microscopic fat is also present. Fat-saturated images will show signal loss in the fatty components with persistence of high signal corresponding to the myeloid component. Out-of-phase images show slight loss of signal in the fatty components. A lipid-rich adrenal adenoma, on the other hand, would reveal more loss of signal intensity on chemical shift imaging.

Reference

Rao P, Kenney PJ, Wagner BJ, Davidson AJ. Imaging and pathologic features of myelolipoma. Radiographics. 1997 Nov-Dec;17(6):1373-85.