My clinical approach
An incidentaloma is never "just an incidental finding". It is an opportunity to identify a functioning tumor or malignancy early. The first evaluation must be comprehensive — not piecemeal.
- Full hormonal screen for every patient — even without clinical symptoms.
- Non-contrast CT for characterization — an incidental contrast-enhanced CT is not enough.
- Multidisciplinary discussion with endocrinology for every MACS, hormonally active or imaging-equivocal finding.
What is an incidentaloma?
An adrenal mass ≥ 1 cm discovered incidentally on imaging performed for another reason. Excludes lesions in patients with known malignancy or clinical suspicion of hormonal disorder.
Epidemiology
- 4-7% on abdominal CT.
- Up to 10% in patients > 70 years.
- Non-functioning benign adenomas ~80%.
- MACS ~5-10%.
- Pheochromocytoma 1.5-7%.
- Adrenocortical carcinoma (ACC) ~2-5%.
- Metastases ~5-15% (especially with known malignancy).
Hormonal workup
Per ESE/ENSAT 2023:
- 1-mg overnight DST — rule out Cushing/MACS. Morning cortisol < 1.8 µg/dL = negative.
- Plasma or 24-h urine metanephrines — rule out pheochromocytoma.
- Aldosterone-renin ratio (ARR) — only in hypertensive or hypokalemic patients.
- DHEA-S, testosterone, estradiol — in suspicious ACC features or clinical symptoms.
Imaging characterization
- Non-contrast CT: HU < 10 → benign adenoma with high confidence.
- HU 10-20: equivocal — washout protocol or chemical-shift MRI.
- HU > 20-30: suspicious for ACC, metastasis, pheochromocytoma.
- Washout: absolute > 60% and relative > 40% at 15 minutes → lipid-poor adenoma.
- Chemical-shift MRI: signal drop in-phase vs. out-of-phase → adenoma.
- FDG-PET/CT for suspicious or large lesions.
Indications for surgery
Absolute indications
- Hormonally active tumor (cortisol, aldosterone, catecholamines, androgens).
- Diameter > 4 cm — increased ACC risk.
- Suspicious imaging (HU > 20, heterogeneity, necrosis, invasion).
- Growth > 5 mm/year on follow-up.
Laparoscopic adrenalectomy is the standard. Open surgery for very large or invasive tumors.
Follow-up
For non-functioning adenomas < 4 cm with clearly benign features, ESE/ENSAT 2023 does not recommend routine repeat imaging. Hormonal tests are repeated periodically if symptoms develop. Equivocal lesions: repeat in 6-12 months.
MACS — mild autonomous cortisol
MACS (post-DST cortisol > 1.8 µg/dL without clinical Cushing) is associated with increased cardiovascular events, diabetes, osteoporosis and mortality. In younger patients with cortisol-related comorbidities, adrenalectomy is considered.
Bottom line: Every adrenal incidentaloma deserves a full hormonal and imaging workup. Correct classification leads to either reassurance or timely surgical treatment.
Frequently Asked Questions (FAQ)
What is an adrenal incidentaloma?
An adrenal mass ≥ 1 cm discovered incidentally on imaging performed for unrelated reasons. Frequency: 4-7% on abdominal CT, increasing with age (~10% in > 70 years).
Are all incidentalomas malignant?
No. Approximately 80% are non-functioning benign adenomas. Per ESE/ENSAT 2023 guidelines, every incidentaloma needs full hormonal and imaging evaluation regardless of patient symptoms.
What tests are needed?
1-mg overnight dexamethasone suppression test (rule out Cushing/MACS), plasma or 24-h urine metanephrines (rule out pheochromocytoma), aldosterone-renin ratio in hypertensive patients (rule out Conn). Imaging: non-contrast CT (HU < 10 = lipid-rich adenoma). If equivocal: washout protocol or MRI.
When is surgery needed?
Tumors > 4 cm, hormonally active, with suspicious imaging features (HU > 20, heterogeneity, irregular margins), or growth on follow-up. Laparoscopic adrenalectomy is the standard approach.
How often should I follow up?
For non-functioning adenomas < 4 cm with typical imaging features, ESE/ENSAT 2023 suggests no routine repeat imaging. Hormonal tests are repeated periodically if symptoms develop.
What is MACS?
Mild Autonomous Cortisol Secretion — biochemical evidence of mild cortisol excess (post-DST cortisol > 1.8 µg/dL) without clinical Cushing. Associated with cardiovascular events, diabetes, osteoporosis and increased mortality. Surgery considered in younger patients with cortisol-related comorbidities.
What does low HU on CT mean?
HU < 10 on non-contrast CT indicates high lipid content, characteristic of benign adenoma. HU > 20-30 raises suspicion for ACC, metastasis, or pheochromocytoma.
Is biopsy safe?
Not routinely recommended. Absolutely contraindicated in pheochromocytoma (risk of hypertensive crisis). Reserved for cases with suspected metastasis from a known extra-adrenal cancer where biopsy will change management.
Related Topics
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A new adrenal finding deserves correct evaluation from the start — complete hormonal workup, dedicated imaging, and multidisciplinary discussion.
References
- Fassnacht M, et al. ESE/ENSAT clinical practice guideline on the management of adrenal incidentalomas (2023) — academic.oup.com
- Sherlock M, et al. Adrenal Incidentaloma — Endocrine Reviews (2020) — academic.oup.com
- NIH State-of-the-Science Conference Statement on Management of the Clinically Inapparent Adrenal Mass — consensus.nih.gov
Medical Review
Dr. Marinos Vasilas, Urologist — Andrologist
Dr. Marinos Vasilas evaluates adrenal incidentalomas in close collaboration with endocrinology and radiology, applying ESE/ENSAT 2023 guidelines for comprehensive hormonal and imaging characterization.
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