Size Ranges for Adrenal Incidentaloma Requiring Further Workup
For adrenal incidentalomas, further workup is recommended for lesions ≥3 cm, with surgical consideration strongly indicated for masses >5 cm due to increased risk of malignancy. 1
Size-Based Management Algorithm
- Lesions <3 cm with benign imaging characteristics (<10 HU on non-contrast CT) generally do not require extensive workup as most are benign adenomas 1, 2
- Lesions 3-5 cm should undergo second-line imaging with either washout CT or chemical shift MRI to better characterize the mass 1, 3
- Lesions >5 cm should be surgically removed due to significantly higher risk of malignancy 1, 2
- Lesions ≥4 cm that are radiologically benign (<10 HU) should undergo repeat imaging in 6-12 months 1, 3
Imaging Characteristics That Warrant Further Evaluation
- Adrenal masses >10 HU on non-contrast CT require additional imaging regardless of size 1, 3
- Inhomogeneous appearance, irregular margins, and lack of clear boundaries are concerning features that warrant additional evaluation 2, 4
- Growth rate >5 mm/year on follow-up imaging is an indication for surgical consideration after repeating functional workup 1, 3
- Growth rate <3 mm/year does not require further imaging or functional testing 1, 3
Hormonal Evaluation
- All adrenal incidentalomas, regardless of size, should undergo hormonal evaluation 3, 4:
- 1 mg overnight dexamethasone suppression test to screen for autonomous cortisol secretion
- Plasma or urinary metanephrines for pheochromocytoma (especially for lesions ≥10 HU)
- Aldosterone/renin ratio for patients with hypertension and/or hypokalemia
Special Considerations
- For patients with history of malignancy, even smaller adrenal lesions warrant closer evaluation as the risk of metastatic disease is significantly higher (25-72% depending on primary tumor type) 1, 4
- Adrenal biopsy should be reserved only for cases where noninvasive techniques are equivocal and there is high suspicion for metastatic disease 1, 4
Common Pitfalls to Avoid
- Relying solely on size criteria for determining malignancy risk - imaging characteristics and growth rate are also important 2, 5
- Failing to perform hormonal evaluation on all adrenal incidentalomas, which can miss subclinical hormone production 3, 6
- Unnecessary follow-up imaging for small (<3 cm) adrenal masses with benign characteristics, leading to increased radiation exposure and patient anxiety 2, 3
- Over-reliance on adrenal washout CT, as approximately 1/3 of pheochromocytomas may washout in the characteristic range of an adenoma, and 1/3 of adrenal adenomas do not washout in the adenoma range 1