What is the management approach for a 1.6 cm lesion in the left adrenal gland?

Management of a 1.6 cm Left Adrenal Lesion

A 1.6 cm adrenal lesion requires initial characterization with unenhanced CT to determine Hounsfield units (HU) and comprehensive hormonal evaluation, but if imaging shows benign features (≤10 HU) and hormones are normal, no further follow-up is needed. 1, 2

Initial Imaging Assessment

• Obtain unenhanced CT immediately if not already performed to measure the lesion's attenuation in Hounsfield units, as this is the most critical determinant of benignity 1, 2

• Lesions measuring ≤10 HU on non-contrast CT are lipid-rich adenomas and definitively benign, requiring no additional imaging workup 1, 2, 3

• If the lesion measures >10 HU, proceed to second-line imaging with either:

  • CT washout protocol (absolute washout ≥60% or relative washout ≥40% indicates benign adenoma) 3
  • Chemical-shift MRI showing signal loss on out-of-phase imaging compared to in-phase imaging (confirms lipid content and benignity) 1, 3

• At 1.6 cm size, this lesion has very low malignancy risk (<5%), as essentially all primary adrenal cortical carcinomas in patients without cancer history are >5 cm 2, 4

Mandatory Hormonal Evaluation

Despite the small size and likely benign imaging, all adrenal incidentalomas require complete hormonal screening to exclude subclinical hormone production, which occurs in approximately 5% of radiologically benign lesions 2, 3

• Perform 1 mg overnight dexamethasone suppression test (or midnight salivary cortisol) to screen for mild autonomous cortisol secretion (MACS) 1, 2

• Measure plasma-free metanephrines or 24-hour urinary metanephrines if the lesion has HU ≥10 or if any signs/symptoms of catecholamine excess exist (hypertension, headaches, palpitations, diaphoresis) 1, 2

• Check aldosterone-to-renin ratio if the patient has hypertension or hypokalemia 1, 2

• Measure DHEAS and testosterone only if there are clinical signs of virilization or if adrenocortical carcinoma is suspected 1

Management Based on Results

If Imaging Shows Benign Features (≤10 HU) AND Hormones Are Normal:

• No further imaging follow-up or functional testing is required for non-functioning adenomas <4 cm with benign imaging characteristics 1, 2, 3

• This represents a strong recommendation with moderate-quality evidence from the most recent 2023 CUA/AUA guidelines 1

If Hormonal Hypersecretion Is Detected:

• Pheochromocytoma: Adrenalectomy is mandatory after appropriate alpha-blockade for 1-3 weeks preoperatively 1, 2

• Aldosterone-secreting adenoma: Unilateral adrenalectomy is indicated, preferably via minimally invasive surgery 1, 2

• Mild autonomous cortisol secretion (MACS): Consider adrenalectomy only in younger patients with progressive metabolic comorbidities (diabetes, hypertension, cardiovascular disease, vertebral fractures) attributable to cortisol excess after shared decision-making; otherwise, annual clinical screening for worsening comorbidities 1

• Overt Cushing's syndrome: Unilateral adrenalectomy of the affected gland 1

If Imaging Is Indeterminate (>10 HU with inadequate washout):

• Repeat imaging in 3-6 months to assess for growth, or consider surgical resection after shared decision-making 1, 3

• Growth <3 mm/year requires no further action, while growth >5 mm/year warrants consideration for adrenalectomy after repeating hormonal workup 3

Critical Pitfalls to Avoid

• Never skip hormonal evaluation even for small, radiologically benign lesions, as subclinical hormone excess occurs in 5% of incidentalomas and can cause significant morbidity 2, 3

• Do not perform adrenal biopsy as part of initial workup; it is only indicated in rare cases where metastatic disease is suspected and pathology would directly change management 1, 2

• Do not assume all small lesions are benign without proper imaging characterization—HU measurement is non-negotiable 1, 2

• Pheochromocytoma must be excluded before any biopsy to prevent potentially fatal catecholamine crisis 1

Special Considerations

• In patients with a history of malignancy, even small adrenal lesions warrant closer evaluation as metastatic disease risk is significantly higher (25-72% depending on primary tumor type) 2

• For younger patients or those concerned about radiation exposure, chemical-shift MRI is an excellent alternative to CT washout protocols 3

• Minimally invasive surgery should be performed when feasible for any indicated adrenalectomy, as it reduces complications compared to open approaches 1