Discussion of Myelolipoma
- Myelolipoma is an uncommon benign tumor composed of mature adipose cells and hematopoietic tissue.
- The prevalence in autopsy series is between 0.08% and 0.2%.
- Typically, myelolipoma arises in the adrenal gland (extra-adrenal myelolipomas are rare).
- Usually asymptomatic and discovered incidentally at cross-sectional imaging.
- Myelolipoma occasionally causes discomfort due to compression or hemorrhage.
 Imaging Findings for Myelolipoma
- Lesions usually have a negative Hounsfield unit value owing to macroscopic fat.
- Because of intermixed hematopoietic tissue, the attenuation is usually higher than that of retroperitoneal fat.
- High-attenuation regions may be seen due to hemorrhage or calcifications.
- At MR imaging, the fatty component is usually hyperintense on T1-weighted images and heterogeneously hyperintense on T2-weighted images due to nonuniform admixture of fat and marrow components.
- This appearance is nonspecific.
- Frequency-selective fat suppression allows the diagnosis of myelolipoma to be confirmed by demonstrating signal loss.
- Chemical shift in-phase/opposed-phase imaging may also be diagnostic by demonstrating india ink or etching artifacts between fat- and water-based components. India ink or etching artifacts are produced at boundaries between fat- and water-based tissues. The reason is that the voxels along those boundaries contain both fat and water protons and hence lose signal on opposed-phase relative to in-phase images.
Patient #1: CT images demonstrate a large left myelolipoma
Patient #2: CT images demonstrate a left myelolipoma with a small amount of marcoscopic fat
 See Also
 External Links
 References for Myelolipoma
- Jose M. Pereira, Claude B. Sirlin, Pedro S. Pinto, and Giovanna Casola. CT and MR Imaging of Extrahepatic Fatty Masses of the Abdomen and Pelvis: Techniques, Diagnosis, Differential Diagnosis, and Pitfalls. RadioGraphics 2005 25: 69-85.