What is the recommended management for a 2.6 cm left adrenal gland nodule with characteristics suggestive of an adenoma, Hounsfield units (HU) much less than 10, and absolute washout over 70%, in an asymptomatic patient with no signs of hormone overproduction and an unremarkable right adrenal gland?

Management of a 2.6 cm Adrenal Adenoma with Benign Imaging Characteristics

This adrenal mass requires no further imaging follow-up or functional testing, as it meets definitive criteria for a benign non-functional adenoma. 1, 2, 3

Rationale for No Further Follow-Up

Your lesion demonstrates all three hallmark features of a benign lipid-rich adenoma:

• Hounsfield units <10 on non-contrast CT (the single best criterion for diagnosing benign adenoma) 1
• Absolute washout >70% (far exceeding the 60% threshold for benignity) 1
• Size <4 cm (2.6 cm falls well below the threshold requiring surveillance) 1, 2

The Canadian Urological Association (endorsed by the American Urological Association) explicitly states that patients with benign non-functional adenomas <4 cm do not require further follow-up imaging or functional testing. 1 This recommendation is echoed by the American College of Radiology, which confirms that masses <10 HU are definitively benign lipid-rich adenomas requiring no further imaging workup. 2, 3

Critical Size Thresholds

The 4 cm cutoff is evidence-based and consistent across multiple guidelines:

• **Masses <3 cm**: In patients without cancer history, only 1.5% are malignant, and all malignancies were >5 cm in the largest series 1
• Masses <4 cm with benign imaging: No surveillance needed 1
• Masses ≥4 cm: Require repeat imaging in 6-12 months even if radiologically benign 1
• Masses >5-6 cm: Should be surgically removed due to higher malignancy risk 1

Hormonal Evaluation Considerations

While imaging confirms benignity, approximately 5% of radiologically benign incidentalomas have subclinical hormone production. 2, 3 However, the question states the patient is asymptomatic with no signs of hormone overproduction. If hormonal screening has not been performed, consider one-time testing for:

• Pheochromocytoma: Plasma or 24-hour urinary metanephrines 1, 3, 4
• Cortisol excess: 1 mg overnight dexamethasone suppression test 4
• Aldosterone excess (only if hypertensive or hypokalemic): Aldosterone-to-renin ratio 3, 4

If hormonal workup is negative, no repeat hormonal testing is needed. 1

Common Pitfalls to Avoid

Do not perform adrenal biopsy - it is contraindicated for suspected benign lesions due to unnecessary risks including tumor seeding and potential hypertensive crisis if an undiagnosed pheochromocytoma is present. 1, 2, 3

Do not order repeat imaging - this increases radiation exposure, patient anxiety, and healthcare costs without clinical benefit for masses meeting all benign criteria. 1, 3

Do not pursue annual surveillance - the ESE guidelines specifically recommend against routine follow-up imaging for radiologically benign adenomas <4 cm, as the rate of malignant transformation is 0% to <1%. 1

Why Washout Criteria Support Benignity

Your lesion's absolute washout >70% provides additional confirmation beyond the HU measurement. The standard threshold is ≥60% absolute washout at 15 minutes for adenoma diagnosis. 1 While approximately one-third of adenomas may not washout in the typical range, your lesion exceeds this threshold substantially, further supporting benignity. 1

Documentation and Patient Communication

Document that this represents a benign non-functional adenoma requiring no further follow-up based on definitive imaging criteria. 1 Reassure the patient that these lesions do not transform into malignancy and do not require monitoring. 1