In this video lecture, we discuss the imaging appearance of adrenal cysts and myelolipomas, as well as differential diagnostic considerations.

Key points include:

• Adrenal cysts typically have density of simple fluid ranging from 20 to -10 Hounsfield units (HU).
• Adrenal pseudocysts may be symptomatic, may have a complicated appearance and may have peripheral calcification.
• The “claw” sign can be helpful in differentiating adrenal from renal masses.
• Gastric diverticula can mimic adrenal cysts but can be differentiated by identifying communication of gastric diverticulum with adjacent stomach, as well as the presence of oral contrast and/or gas with the diverticulum.
• Adrenal myelolipomas are benign neoplasms that have varying degrees of macroscopic fat and hematopoietic soft tissue elements.
• Fat density within myelolipomas on CT ranges from -30 to -90 HU.
• Up to 30% of myelolipomas contain small calcifications.
• Unlike myelolipomas, malignant retroperitoneal sarcomas are usually ill-defined and displace or invade adjacent structures.
• Because myelolipomas contain macroscopic fat, they show greater signal loss (darkening) on fat-saturated images compared to T1 opposed-phase chemical shift images.
• Conversely, lipid-rich adrenal adenomas contain microscopic fat (also known as intracellular, intracytoplasmic, or intravoxel fat) and therefore show greater signal loss on T1 opposed-phase images than on fat-saturated images.

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