Follow-Up for 21 mm Adrenal Adenoma in 67-Year-Old Female
No further imaging or functional testing is required if this lesion has been confirmed as a benign, non-functional adenoma less than 4 cm. 1
Initial Characterization Required
Before discontinuing follow-up, confirm the following characteristics have been established:
Imaging Confirmation of Benign Features
- Unenhanced CT must show ≤10 Hounsfield Units (HU) to definitively classify as benign adenoma 1, 2
- Lesion should be homogeneous with well-defined margins 3
- If HU >10, washout CT or chemical shift MRI must have confirmed benign characteristics before observation 3
Hormonal Evaluation Must Be Complete
- 1 mg overnight dexamethasone suppression test (cortisol post-dexamethasone should be ≤50 nmol/L or ≤1.8 µg/dL) 2
- Plasma aldosterone-to-renin ratio if patient has hypertension or hypokalemia 4
- Plasma or 24-hour urinary metanephrines only if lesion is >10 HU or patient has signs of catecholamine excess 5, 4
No Follow-Up Needed If Criteria Met
The 2023 CUA/AUA guidelines provide strong evidence (moderate quality) that benign non-functional adenomas <4 cm require no further follow-up imaging or functional testing. 1 This 21 mm (2.1 cm) lesion falls well below the 4 cm threshold where malignancy risk increases significantly.
Critical Exceptions Requiring Follow-Up
Size-Based Exception
- If the lesion is ≥4 cm (40 mm), repeat imaging in 6-12 months is required even if radiologically benign, as most pheochromocytomas and adrenocortical carcinomas were >4 cm at diagnosis 1, 3
- This patient's 21 mm lesion does not meet this threshold
Growth Rate Exception
- If any prior imaging showed growth >5 mm/year, adrenalectomy should be considered after repeating functional work-up 1, 5
- Growth of 3-5 mm/year warrants continued surveillance with repeat imaging in 6-12 months 5
- Growth <3 mm/year requires no further follow-up 1, 5
Functional Status Exception
- If mild autonomous cortisol secretion (MACS) is present (post-dexamethasone cortisol >50 nmol/L), annual clinical screening for metabolic comorbidities is required 1
- Younger patients with MACS and progressive metabolic comorbidities may be considered for adrenalectomy 1
Common Pitfalls to Avoid
- Do not assume benign appearance eliminates need for initial hormonal evaluation - approximately 5% of radiologically benign incidentalomas have subclinical hormone production requiring treatment 3
- Do not perform adrenal biopsy - this is rarely indicated and carries risks, reserved only for suspected metastatic disease where results would change management 1, 3
- Do not continue unnecessary surveillance once benign, non-functional status is confirmed for lesions <4 cm, as this increases radiation exposure, patient anxiety, and healthcare costs 4
- Do not apply these recommendations to patients with history of extra-adrenal malignancy - up to 50% of adrenal masses in cancer patients represent independent adrenal pathology rather than metastases, requiring different evaluation 3, 6