How should a 1.8 cm left adrenal adenoma be evaluated and managed?

Management of a 1.8 cm Left Adrenal Adenoma

A 1.8 cm left adrenal adenoma requires comprehensive hormonal evaluation to exclude functional disease, followed by initial imaging characterization with non-contrast CT; if the lesion demonstrates benign features (≤10 HU) and is hormonally inactive, no further imaging follow-up is needed. 1

Initial Imaging Characterization

• Non-contrast CT (NCCT) is the first-line imaging study to characterize the adrenal mass if not already performed, measuring attenuation in Hounsfield Units (HU). 2

• Lesions with NCCT attenuation ≤10 HU are definitively benign adenomas and require no additional imaging workup. 1, 2

• For lesions with attenuation 11-20 HU and <4 cm in size, proceed with second-line imaging using either chemical shift MRI, adrenal washout CT protocol, or PET-CT based on institutional availability. 2 Alternatively, follow-up imaging at 12 months is acceptable. 2

• Lesions >20 HU or those that are heterogeneous carry relevant malignancy risk and should be discussed at a multidisciplinary conference for consideration of surgical resection. 2

Mandatory Hormonal Evaluation

All patients with adrenal incidentalomas require biochemical screening regardless of symptoms, as hormone excess is frequently subclinical. 2, 3

Cortisol Screening (Required for All Patients)

• Perform 1 mg overnight dexamethasone suppression test as the preferred screening method for autonomous cortisol secretion. 1, 2

• Serum cortisol >1.8 mcg/dL (>50 nmol/L) post-dexamethasone indicates autonomous cortisol secretion and warrants evaluation for cortisol-related comorbidities including hypertension, diabetes, and hyperlipidemia. 1, 2, 4

• Mild autonomous cortisol secretion (MACS) is associated with increased cardiovascular morbidity and metabolic abnormalities, making screening essential even in asymptomatic patients. 2, 3

Pheochromocytoma Screening

• Screen with plasma metanephrines or 24-hour urinary metanephrines if the lesion shows >10 HU on non-contrast CT or if any signs/symptoms of catecholamine excess are present. 1

• Screening can be omitted only if the lesion is an unequivocal adenoma (<10 HU) with no adrenergic symptoms. 1

Primary Aldosteronism Screening

• Measure aldosterone-to-renin ratio in all patients with hypertension and/or hypokalemia. 1, 2

• If primary aldosteronism is confirmed biochemically, adrenal venous sampling (AVS) is mandatory before considering adrenalectomy to determine lateralization. 1, 5

Additional Testing for Suspected Malignancy

• If clinical features or imaging suggest adrenocortical carcinoma (ACC), measure sex hormones and steroid precursors including DHEA-S, 17-hydroxyprogesterone, and androstenedione. 1, 2

Management Based on Functional Status and Size

Non-Functional Benign Adenoma <4 cm

• If the 1.8 cm lesion is radiologically benign (≤10 HU) and hormonally inactive, no further imaging follow-up or functional testing is required. 1 This represents the most common scenario and allows discharge from surveillance. 1

Functional Adenomas Requiring Surgery

• Unilateral cortisol-secreting masses with clinically apparent Cushing's syndrome require unilateral adrenalectomy, preferably via minimally invasive surgery. 1

• Younger patients with mild autonomous cortisol secretion and progressive metabolic comorbidities attributable to cortisol excess may be considered for adrenalectomy after shared decision-making. 1 Those managed non-surgically require annual clinical screening for worsening comorbidities. 1

• Confirmed aldosterone-producing adenomas and pheochromocytomas mandate adrenalectomy, with minimally invasive approaches preferred when feasible. 1

Indeterminate Lesions

• For lesions that remain indeterminate after second-line imaging (11-20 HU, <4 cm), management options include repeat imaging in 3-6 months versus surgical resection based on shared decision-making. 1, 2

• Lesions growing >5 mm/year warrant repeat functional workup and consideration of adrenalectomy. 1, 2

• Lesions growing <3 mm/year require no further imaging follow-up. 1

Special Considerations

Age-Related Risk Stratification

• Patients <40 years old have higher risk of malignancy or clinically relevant hormone excess and should undergo urgent assessment with MRI preferred over CT. 2 Surgical resection should be considered for lesions not characteristically benign on imaging. 2

• Even benign-appearing lesions in patients <40 years may warrant single follow-up imaging at 12 months. 2

Patients with Extra-Adrenal Malignancy

• Exclude pheochromocytoma biochemically before considering biopsy, even when metastasis is suspected, as pheochromocytomas can mimic metastases and cause significant morbidity if biopsied. 2

• Adrenal biopsy should only be performed when histologic diagnosis would alter management and after pheochromocytoma and ACC have been excluded. 1, 2

Common Pitfalls to Avoid

• Never assume a small adrenal mass is non-functional without biochemical testing—up to 30-50% of incidentalomas demonstrate mild autonomous cortisol secretion. 3

• Do not perform adrenal venous sampling for cortisol-producing adenomas—imaging combined with biochemical testing is sufficient for lateralization. 5 AVS is reserved exclusively for primary aldosteronism. 5

• Avoid routine biopsy of adrenal incidentalomas—it risks tumor seeding in ACC and catastrophic hypertensive crisis in undiagnosed pheochromocytoma. 1

• Do not discharge patients with autonomous cortisol secretion without screening for and managing associated metabolic comorbidities (hypertension, diabetes, hyperlipidemia). 2, 4