What is the management approach for a 1.5 cm adrenal (suprarenal) mass?

Management of a 1.5 cm Suprarenal Mass

A 1.5 cm adrenal mass requires initial hormonal evaluation to exclude functional tumors, followed by imaging characterization with unenhanced CT to measure Hounsfield units; if the mass is non-functional and demonstrates benign features (HU ≤10), no further follow-up imaging or functional testing is needed. 1, 2

Initial Hormonal Assessment

All patients with adrenal incidentalomas, regardless of size or benign appearance on imaging, require initial hormonal screening because approximately 5% of radiologically benign incidentalomas have subclinical hormone production that requires treatment 3, 4:

• Perform a 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion (mild autonomous cortisol secretion/MACS) 1, 4
• Measure plasma or 24-hour urinary metanephrines to exclude pheochromocytoma 4
• Check aldosterone-to-renin ratio only if the patient has hypertension and/or hypokalemia 3, 4

Critical pitfall: Skipping hormonal evaluation can lead to undiagnosed pheochromocytoma, which can cause life-threatening hypertensive crisis during any future surgical procedure 4

Imaging Characterization

Obtain unenhanced CT to measure Hounsfield units (HU) 3, 4:

• If HU ≤10: The mass is definitively a benign lipid-rich adenoma and requires no further imaging 3, 4
• If HU >10: Perform second-line imaging with either washout CT or chemical shift MRI to confirm benign characteristics 3

The mass should demonstrate homogeneous appearance with well-defined margins to be considered benign 3

Management Algorithm Based on Results

If Non-Functional and Benign-Appearing (HU ≤10):

No further follow-up imaging or functional testing is required 1, 2, 3. This strong recommendation is based on moderate-quality evidence showing that small (<4 cm) benign non-functional adenomas have a 0% to <1% risk of malignant transformation 2

If Functional Abnormality Detected:

• Pheochromocytoma or aldosterone-secreting adenoma: Adrenalectomy is indicated, preferably via minimally invasive surgery when feasible 1
• Mild autonomous cortisol secretion (MACS): Consider adrenalectomy only in younger patients with progressive metabolic comorbidities attributable to cortisol excess after shared decision-making; otherwise, perform annual clinical screening for new or worsening comorbidities 1
• Clinically apparent Cushing's syndrome: Unilateral adrenalectomy of the affected gland is required 1

Size-Specific Considerations

For this 1.5 cm mass, the size alone is reassuring 1, 2:

• Most small (<3 cm) incidentally discovered adrenal masses in patients without a history of malignancy are benign, and extensive workup is usually not justified 1
• The risk for primary adrenal cortical carcinoma in the general population is only 0.06% 1
• Lesions <4 cm that are benign and non-functional require no further surveillance 1, 2, 3

Special Population Exception

If the patient has a history of extra-adrenal malignancy, the approach differs significantly 1, 3:

• The rate of metastatic disease to the adrenal gland is 25-72% depending on the primary tumor type 1, 3
• Bronchogenic carcinoma, renal carcinoma, and melanoma have particularly high rates of adrenal metastases 1
• In this population, even smaller adrenal lesions are suspect and require closer evaluation 1

Common Pitfalls to Avoid

• Do not perform adrenal mass biopsy routinely for the workup of an adrenal incidentaloma; this is rarely indicated, carries unnecessary risks, and should be reserved only for cases where noninvasive techniques are equivocal with high suspicion for metastatic disease 1, 3, 4
• Avoid unnecessary repeated imaging for small adrenal masses with benign characteristics, as this leads to increased radiation exposure, patient anxiety, and healthcare costs 2
• Do not skip the initial hormonal evaluation even if the mass appears benign on imaging, as functional abnormalities occur in approximately 5% of cases and require treatment 3, 4