What is the recommended evaluation and management for an incidentally discovered adrenal adenoma?

Management of Adrenal Adenoma

All incidentally discovered adrenal adenomas require comprehensive hormonal evaluation regardless of size or imaging appearance, followed by a management strategy determined by functional status, size, and imaging characteristics. 1

Initial Hormonal Evaluation (Mandatory for All Patients)

Every patient with an adrenal adenoma must undergo complete biochemical screening before any management decisions: 1

• Perform a 1 mg overnight dexamethasone suppression test (give 1 mg dexamethasone at 11 PM, measure serum cortisol at 8 AM) to screen for autonomous cortisol secretion in all patients. 2, 3

  • Cortisol ≤50 nmol/L (≤1.8 µg/dL) excludes hypersecretion 3, 4
  • Cortisol 51-138 nmol/L suggests possible autonomous secretion 3
  • Cortisol >138 nmol/L indicates cortisol hypersecretion 3

• Measure plasma free metanephrines or 24-hour urinary metanephrines/normetanephrines to exclude pheochromocytoma before any biopsy or surgery. 2, 3, 5

• Check aldosterone-to-renin ratio only if the patient has hypertension and/or hypokalemia to screen for primary aldosteronism (ratio >20 ng/dL per ng/mL/hr is diagnostic). 2, 3

• Do not routinely measure DHEA-S, androstenedione, testosterone, 17-hydroxyprogesterone, or estradiol unless there are specific clinical signs of virilization or feminization. 3

Imaging Characterization

Obtain non-contrast CT with Hounsfield unit (HU) measurement as the mandatory first imaging test to separate benign lipid-rich adenomas from indeterminate masses. 2, 5

Imaging-Based Risk Stratification:

• HU ≤10 on non-contrast CT: Confirms benign lipid-rich adenoma; no further imaging characterization needed 2, 4

• HU 10-20: Obtain second-line imaging with either washout CT or chemical-shift MRI 2

• HU >20: Requires multidisciplinary review (endocrinology, surgery, radiology) before further intervention 2

Critical Imaging Caveat:

Approximately one-third of benign adenomas fail to demonstrate typical washout (≥60%), meaning low washout does not definitively indicate malignancy. Conversely, some malignant masses and one-third of pheochromocytomas can show adenoma-like washout, making functional testing mandatory regardless of imaging. 2

Management Algorithm Based on Size and Functional Status

Definitive Surgical Indications (Regardless of Size):

Adrenalectomy is unequivocally indicated for: 2, 3, 5

• Confirmed pheochromocytoma (any size)
• Aldosterone-producing adenoma with unilateral secretion confirmed by adrenal vein sampling
• Clinically apparent Cushing's syndrome from unilateral cortisol-secreting mass
• Use minimally invasive surgery when feasible for functional tumors and suspected adrenocortical carcinoma that can be resected without capsule rupture 2, 5

Size-Based Management for Non-Functional Adenomas:

Lesions <4 cm with benign imaging (HU ≤10): 2, 3

• No additional imaging or functional testing required after initial workup
• No routine follow-up needed

Lesions ≥4 cm with benign imaging (HU ≤10): 2, 3, 5

• Repeat imaging in 6-12 months
• If growth <3 mm/year: No further imaging needed 2
• If growth >5 mm/year: Repeat hormonal evaluation and consider adrenalectomy 2, 3

Indeterminate non-functional lesions (HU >10, <4 cm): 2

• Preferred approach: Repeat imaging in 3-6 months
• Alternative: Surgical resection after shared decision-making
• If growth >5 mm/year on surveillance: Repeat functional workup and consider adrenalectomy

Lesions 4-6 cm with indeterminate features: 2

• Repeat imaging in 3-6 months initially
• If enlarging >1 cm in 1 year: Proceed to adrenalectomy for suspected carcinoma

Lesions >6 cm: 2

• Strongly consider surgical resection regardless of washout characteristics due to higher malignancy risk

Critical Pitfalls to Avoid

Never perform adrenal biopsy for routine workup of incidentalomas. Biopsy is rarely indicated and carries risks of tumor seeding, hemorrhage, and precipitating hypertensive crisis if an undiagnosed pheochromocytoma is present. 2, 3, 5

Never proceed with any intervention before excluding pheochromocytoma. Undiagnosed pheochromocytoma can cause life-threatening hypertensive crisis during surgery or biopsy. 2

Do not skip initial hormonal evaluation even for radiologically benign-appearing lesions. Approximately 5% of radiologically benign incidentalomas harbor subclinical hormone production requiring treatment. 5

Special Populations Requiring Expedited Evaluation

Young adults (<40 years), children, and pregnant patients require expedited evaluation because adrenal lesions are more likely malignant in these populations. Use low-dose CT or chemical-shift MRI to minimize radiation exposure. 5

Patients with history of extra-adrenal malignancy require closer evaluation even for smaller lesions, as metastatic disease to the adrenal gland occurs in 25-72% depending on primary tumor type. 5

Bilateral Adrenal Adenomas

Each lesion should be characterized separately using the same algorithm as for unilateral masses. Additionally, measure serum 17-hydroxyprogesterone to exclude congenital adrenal hyperplasia, and assess for adrenal insufficiency if bilateral infiltrative disease, metastases, or hemorrhage is suspected. 3, 5