What is the management for an adult patient with a non-functioning adrenal adenoma that has grown from 2.5 cm to 3.5 cm over 8 years?

Management of Non-Functioning Adrenal Adenoma with 1 cm Growth Over 8 Years

Direct Recommendation

This adenoma requires repeat imaging in 6-12 months but does NOT meet criteria for surgical intervention, as the growth rate of 1.25 mm/year is well below the 5 mm/year threshold that would warrant adrenalectomy. 1

Growth Rate Analysis

The critical decision point hinges on annual growth rate calculation:

• Your adenoma grew 10 mm over 8 years = 1.25 mm/year
• The 2023 CUA/AUA guidelines explicitly state that adrenalectomy should only be considered for growth >5 mm/year 1
• Growth <3 mm/year requires no further imaging follow-up or functional testing 1
• Your growth rate falls in the intermediate zone (between 3-5 mm/year), warranting continued surveillance 2

Required Confirmatory Steps Before Proceeding

1. Verify Benign Imaging Characteristics

You must confirm this is truly a benign adenoma by checking:

• Unenhanced CT attenuation ≤10 Hounsfield Units (HU) - this is diagnostic of benign lipid-rich adenoma 2, 3
• If attenuation is >10 HU, perform either contrast washout CT (>60% washout at 15 minutes indicates benign) or chemical shift MRI 1, 2
• Ensure the mass is homogeneous with well-defined margins 4, 3

2. Repeat Functional Testing

Even though initially non-functioning, you must repeat hormonal evaluation now because autonomous hormone secretion can develop over time:

• 1 mg overnight dexamethasone suppression test (cortisol should be ≤50 nmol/L or ≤1.8 µg/dL) 3
• Plasma-free metanephrines or 24-hour urinary metanephrines to exclude pheochromocytoma 1, 4
• Plasma aldosterone and renin activity to exclude hyperaldosteronism 1, 4

This repeat testing is critical because mild autonomous cortisol secretion (MACS) occurs in a significant proportion of incidentalomas and carries increased morbidity/mortality risk 3.

Surveillance Strategy

Obtain repeat imaging in 6-12 months 1, 2:

• If growth remains <3 mm on this follow-up scan, discontinue all surveillance - no further imaging or functional testing required 1
• If growth accelerates to >5 mm/year on follow-up, then consider adrenalectomy after repeating functional workup 1

Size Considerations

Your adenoma is now 3.5 cm, which is relevant:

• Adenomas <4 cm with confirmed benign characteristics and no hormonal activity do not require surgery based on size alone 1, 4
• The traditional 4 cm cutoff for increased malignancy risk does not apply when imaging clearly demonstrates benign features (≤10 HU) 1, 3
• Homogeneous lesions with HU ≤10 are benign regardless of size 3

Critical Pitfalls to Avoid

• Do not operate based on growth alone - the 1.25 mm/year rate is far below surgical thresholds and likely represents measurement variability 1
• Do not skip repeat hormonal testing - assuming continued non-function without verification can miss developing MACS 3
• Do not use the older 3 cm surgical threshold - outdated 1989 data suggested surgery for all tumors >3 cm 5, but modern imaging allows confident identification of benign lesions that can be safely observed 3

When Surgery Would Be Indicated

Adrenalectomy would only be appropriate if:

• Growth accelerates to >5 mm/year on subsequent imaging 1
• Repeat functional testing reveals new hormone hypersecretion 1, 3
• Imaging characteristics change to suggest malignancy (irregular margins, heterogeneity, HU >20) 3