General Considerations

• Rare, usually non-functioning tumors found incidentally most often in males aged 40-60
• Benign tumors composed of fat and hemopoietic cells enclosed by pseudocapsule
• Usually occurs in adrenal gland but may be extra-adrenal in 15%

Clinical Findings

• Almost always asymptomatic
• Most are discovered incidentally during a CT scan for other reasons
  • Adrenal masses are discovered incidentally in about 2.5-5% of abdominal CT scans
• May be painful if there is hemorrhage

Imaging Findings

• Unilateral
• Usually small (<4 cm)
  • May be large in size (~10 com)
• Hemorrhage is more common in larger lesions
• Calcifications can occur in ¼ from prior hemorrhage
• CT
• Fatty mass of -30 to -115 HU
• Fat interspersed with higher attenuation marrow-like elements
• US
• Mostly hyperechoic mass with interspersed hypoechoic regions
• MRI
• Heterogeneously high signal on T1
• Intermediate intensity similar to spleen on T2
• In opposed phase, there is a drop in signal intensity

Differential Diagnosis

• Adrenal cysts
  • Water density with thin wall
• Adrenal adenomas
  • Most are fat containing with densities of <10 HU
• Density measurements before and after contrast administration can be used
• Enhancement washout (HU portal venous phase minus HU delayed phase)/ HU portal venous phase x 100
• If value is > 50%, adrenal adenoma
• Sensitivity of 93% and specificity 98%

Treatment

• Conservative with follow-up to determine if there is enlargement for masses >4 cm
• Symptomatic masses are usually surgically removed

Complications

• Occasionally associated with endocrine disturbances
  • Cushing’s syndrome
• Conn’s syndrome
• Addison’s disease
• Acute hemorrhage may be associated with increase in size

 

 

Adrenal myelipoma. Contrast-enhanced axial CT scan image through the upper abdomen reveals a large, partially fat-containing mass in the left adrenal glad (white arrow). The mass has a thin capsule surrounding it. A portion of the normal right adrenal is seen (red arrow).
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