Management of Small Adrenal Masses

Initial Evaluation and Diagnosis

The American College of Radiology recommends that 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 1, 2
Initial hormonal screening is necessary for all patients with adrenal incidentalomas, regardless of size or benign appearance on imaging, because approximately 5% of radiologically benign incidentalomas have subclinical hormone production that requires treatment 3, 4
The American Urological Association suggests performing a 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion (mild autonomous cortisol secretion/MACS) 1, 4
Measurement of plasma or 24-hour urinary metanephrines is recommended to exclude pheochromocytoma 4
The aldosterone-to-renin ratio should be checked only if the patient has hypertension and/or hypokalemia 3, 4

Unenhanced CT should be obtained 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, second-line imaging with either washout CT or chemical shift MRI should be performed to confirm benign characteristics 3

For non-functional and benign-appearing masses (HU ≤10), no further follow-up imaging or functional testing is required, based on moderate-quality evidence showing a 0% to <1% risk of malignant transformation 1, 2, 3
For functional abnormalities, adrenalectomy is indicated for pheochromocytoma or aldosterone-secreting adenoma, preferably via minimally invasive surgery when feasible 1
For mild autonomous cortisol secretion (MACS), adrenalectomy should be considered only in younger patients with progressive metabolic comorbidities attributable to cortisol excess after shared decision-making 1

Most small (<3 cm) incidentally discovered adrenal masses in patients without a history of malignancy are benign, and extensive workup is usually not justified 5
Lesions <4 cm that are benign and non-functional require no further surveillance 1, 2, 3
The risk for primary adrenal cortical carcinoma in the general population is only 0.06% 5

If the patient has a history of extra-adrenal malignancy, the approach differs significantly, with a higher suspicion for metastatic disease 5, 3
The rate of metastatic disease to the adrenal gland is 25-72% depending on the primary tumor type 5, 3

Adrenal mass biopsy should not be performed routinely for the workup of an adrenal incidentaloma, as this is rarely indicated and carries unnecessary risks 5, 3, 4
Unnecessary repeated imaging for small adrenal masses with benign characteristics should be avoided, as this leads to increased radiation exposure, patient anxiety, and healthcare costs 2
Initial hormonal evaluation should not be skipped, even if the mass appears benign on imaging, as functional abnormalities occur in approximately 5% of cases and require treatment 3, 4