How should I manage a patient with a 1.7 cm adrenal incidentaloma when my facility lacks adrenal imaging?

Managing a 1.7 cm Adrenal Incidentaloma Without On-Site Imaging

Transfer the patient to a facility with non-contrast CT capability to measure Hounsfield units, as this is the essential first step that cannot be bypassed—without it, you cannot determine if the mass is benign or requires further workup. 1, 2

Why Imaging Cannot Be Deferred

• Non-contrast CT measurement of Hounsfield units (HU) is the mandatory initial imaging test that distinguishes benign lipid-rich adenomas (HU ≤10) from indeterminate masses requiring additional investigation. 1, 3
• A lesion measuring ≤10 HU is definitively benign and requires no further imaging workup, while lesions >10 HU need second-line imaging with washout CT or chemical-shift MRI. 2, 3, 4
• Without HU measurement, you cannot safely determine whether this 1.7 cm mass is benign or potentially malignant, leaving you unable to make evidence-based management decisions. 3, 5

Complete Hormonal Workup While Arranging Transfer

While coordinating transfer for imaging, initiate the complete hormonal evaluation, as all patients with adrenal incidentalomas require biochemical screening regardless of size or presumed benign appearance. 1, 4

Mandatory Screening Tests

• Perform 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion (cortisol >50 nmol/L or >1.8 µg/dL is abnormal). 1, 5
• Measure plasma metanephrines or 24-hour urinary metanephrines to exclude pheochromocytoma—this is critical before any biopsy or surgery to prevent life-threatening hypertensive crisis. 1, 2
• Check aldosterone-to-renin ratio only if the patient has hypertension and/or hypokalemia, as screening is not indicated in normotensive patients with normal potassium. 1, 2

Size-Based Risk Assessment

• At 1.7 cm, this mass falls well below the 4 cm threshold where malignancy risk becomes substantial. 1, 6, 5
• Most adrenal masses <3 cm in patients without extra-adrenal malignancy are benign, and extensive workup beyond hormonal screening and HU measurement is typically not justified. 3, 4
• The risk of primary adrenocortical carcinoma in the general population is only 0.06%. 4

Management Algorithm After Imaging

If HU ≤10 (Benign Adenoma)

• No further imaging or follow-up is required if the mass is non-functional on hormonal testing. 2, 4, 5
• This represents a definitive benign lipid-rich adenoma with 0% to <1% risk of malignant transformation. 4

If HU >10 (Indeterminate)

• Obtain second-line imaging with either washout CT or chemical-shift MRI to further characterize the lesion. 1, 2
• For washout CT, calculate relative percentage washout: [1 – (delayed HU / dynamic HU)] × 100%; washout >50% indicates benign adenoma. 3
• If the lesion remains indeterminate and non-functional after complete workup, use shared decision-making to choose between repeat imaging in 3-6 months versus surgical resection. 2

Surgical Indications

Adrenalectomy is definitively indicated if hormonal testing reveals:

• Confirmed pheochromocytoma (any size). 1, 2
• Aldosterone-producing adenoma with unilateral secretion confirmed by adrenal vein sampling. 1, 2
• Clinically apparent Cushing's syndrome from unilateral cortisol-secreting mass. 1
• Minimally invasive surgery should be performed when feasible for functional tumors. 1, 2

Critical Pitfalls to Avoid

• Never perform adrenal biopsy for routine workup—it is rarely indicated and carries risks of tumor seeding, hemorrhage, and hypertensive crisis if pheochromocytoma is undiagnosed. 1, 2, 3
• Never proceed with any intervention before excluding pheochromocytoma, as undiagnosed pheochromocytoma can cause life-threatening complications during surgery or biopsy. 2, 6, 7
• Do not skip hormonal evaluation even if imaging appears benign, as approximately 5% of radiologically benign incidentalomas have subclinical hormone production requiring treatment. 4

Multidisciplinary Review Triggers

Maintain a low threshold for multidisciplinary consultation (endocrinology, surgery, radiology) if:

• Imaging is not consistent with a benign lesion (atypical HU, inhomogeneity). 1, 2
• Evidence of hormone hypersecretion is found on biochemical testing. 1, 2
• The tumor shows significant growth (>5 mm/year) on follow-up imaging. 1, 2