Synonym: Adrenocortical adenoma

Varies from 2-5 cm, typically < 3 cm, bilateral in 10%

Can be bilateral (10%)

Nonspecific sonographic appearance

Well-circumscribed, solid, oval-shaped mass

Usually homogeneous and hypoechoic

Atypically can appear more heterogeneous, but necrosis is rare in small adenomas

Necrosis is seldom seen in small adenoma

May suggest diagnosis based on US; however, no specific sonographic features distinguish adenomas from other adrenal lesions

Typically small, smoothly marginated, homogeneous, and hypoechoic

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  Size is particularly important: Smaller adrenal lesions tend to be benign; > 4 cm more likely malignant

  
  
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  Size stability over 12 months supports benignity

Smaller lesions are seen with Conn syndrome, usually < 2 cm (20% < 1 cm)

CT and MR: Best imaging modalities to confirm diagnosis

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  Lipid-rich adenomas are best characterized with NECT or chemical shift MR

  
  
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  Lipid-poor adenomas can be characterized with CECT with 10-min delayed-phase imaging

T1WI: Chemical shift MR can confirm presence of intracellular lipid

Lipid-rich adenomas (70-90%): Attenuation < 10 HU is characteristic and diagnostic

Hypovascular on color Doppler

Adrenal metastases

Adrenal hemorrhage

Pheochromocytoma

Classified as nonfunctioning vs. functioning

70% show high intracytoplasmic lipid content: “lipid rich”

More commonly detected as incidental finding

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  Increased detection in recent years due to greater imaging utilization, > 90% of all incidentalomas

15% are functional and produce hormones

Accounts for > 90% of all incidentalomas

Functioning adenomas: Cushing syndrome, Conn syndrome, or virilization syndromes

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  Cushing syndrome, Conn syndrome, or virilization syndromes

Hypertension and weakness with Cushing and Conn syndrome

Benign vs. malignant: Consider size and stability

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  Comparison with any available prior imaging may help to establish stability over 12 month period and avoid unnecessary additional testing

Attenuation < 10 HU on NECT → lipid-rich adenoma

Signal drop on T1 out-of-phase MR → lipid-rich adenoma

> 60% absolute washout on 10-min delayed-phase CECT → lipid-rich and lipid-poor adenomas

Size and stability are helpful clues to diagnosis

CT or MR required for confirmation