Adrenal Cysts and Myelolipomas

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

Key points include:
1) Adrenal cysts typically have density of simple fluid ranging from 20 to -10 Hounsfield units (HU).
2) Adrenal pseudocysts may be symptomatic, may have a complicated appearance and may have peripheral calcification.
3) The “claw” sign can be helpful in differentiating adrenal from renal masses.
4) 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.
5) Adrenal myelolipomas are benign neoplasms that have varying degrees of macroscopic fat and hematopoietic soft tissue elements.
6) Fat density within myelolipomas on CT ranges from -30 to -90 HU.
7) Up to 30% of myelolipomas contain small calcifications.
8) Unlike myelolipomas, malignant retroperitoneal sarcomas are usually ill-defined and displace or invade adjacent structures.
9) Because myelolipomas contain macroscopic fat, they show greater signal loss (darkening) on fat-saturated images compared to T1 opposed-phase chemical shift images.
10) 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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