What is the next step in managing a benign adrenal adenoma that has grown from 2.5 cm to 2.8 cm?

Management of Benign Adrenal Adenoma Growing from 2.5 cm to 2.8 cm

For a benign adrenal adenoma that has grown 3 mm (from 2.5 cm to 2.8 cm), repeat imaging in 6-12 months is recommended, as this growth rate (<5 mm/year) does not meet the threshold for surgical intervention. 1

Growth Rate Assessment

The critical threshold for concerning growth is >5 mm per year, which would prompt consideration for adrenalectomy after repeating functional workup. 1 Your adenoma has grown only 3 mm, which falls below this threshold and indicates:

• Growth <3 mm/year requires no further imaging follow-up or functional testing 1
• Growth between 3-5 mm/year warrants continued surveillance with repeat imaging in 6-12 months 1
• Your 3 mm growth over an unspecified timeframe likely represents stable disease requiring only routine follow-up 1

Size Considerations

At 2.8 cm, this adenoma remains in the low-risk category:

• Benign-appearing adenomas <4 cm with confirmed benign imaging characteristics require no further follow-up if they remain unchanged 1, 2
• The risk of malignancy in adenomas <3 cm is extremely low, with studies showing only 1.5% malignancy rate in patients without prior cancer history, and all malignant lesions were >5 cm 1
• Adenomas between 2.5-4 cm that are radiologically benign (<10 HU on unenhanced CT) and non-functional can be safely observed 1, 2

Required Confirmatory Steps

Before concluding observation is appropriate, ensure the following have been completed:

Imaging Characteristics Verification

• Confirm attenuation ≤10 HU on non-contrast CT, which is diagnostic of benign adenoma 1
• If attenuation is >10 HU, perform either contrast washout CT (≥60% absolute washout at 15 minutes indicates benign) or chemical shift MRI (signal drop-out confirms lipid-rich adenoma) 1
• Verify homogeneous appearance with well-defined margins and no aggressive features (heterogeneity, irregular margins, local invasion) 1

Functional Assessment

• All adrenal incidentalomas require hormonal evaluation regardless of size or imaging appearance 1, 2
• Screen for subclinical Cushing syndrome with 1 mg overnight dexamethasone suppression test or 2-3 midnight salivary cortisol measurements 1, 2
• Measure fractionated plasma-free metanephrines to exclude pheochromocytoma 1, 2
• In hypertensive patients, check plasma aldosterone concentration and plasma renin activity 1, 2

Surveillance Strategy

If the adenoma is confirmed benign and non-functional:

• Repeat imaging in 6-12 months to document stability 1
• If growth remains <3 mm on follow-up imaging, discontinue surveillance as no further imaging or functional testing is required 1
• If growth is 3-5 mm, continue surveillance with repeat imaging in another 6-12 months 1

When to Consider Surgery

Adrenalectomy should be considered only if: 1

• Growth exceeds 5 mm/year on follow-up imaging (after repeating functional workup) 1
• Development of hormonal hypersecretion on repeat testing 1, 2
• Development of aggressive imaging features (heterogeneity, irregular margins, loss of lipid content) 1
• Growth to ≥4 cm with indeterminate features 1

Critical Pitfalls to Avoid

• Do not pursue surgery for minimal growth (<5 mm/year), as this leads to unnecessary procedures and patient harm 1, 2
• Do not skip hormonal evaluation even with benign imaging, as 5-23% of incidentalomas have subclinical hormone excess 1, 2, 3
• Do not perform adrenal biopsy unless there is high suspicion for metastatic disease from known extra-adrenal malignancy and pheochromocytoma has been excluded 1
• Be aware that while extremely rare, transformation from benign adenoma to adrenocortical carcinoma has been reported after many years, though this should not alter standard surveillance protocols 4