Myelolipoma

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[edit] 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.

[edit] Imaging Findings for Myelolipoma

[edit] CT

  • 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.

[edit] MRI

  • 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.

[edit] 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

[edit] See Also

[edit] External Links

[edit] References for Myelolipoma