Adrenal Incidentalomas: How to Evaluate and When Surgery Is Needed

When a scan for something else - like a back pain or abdominal discomfort - turns up an unexpected lump on the adrenal gland, it’s called an adrenal incidentaloma. It sounds scary, but here’s the truth: about 80% of these are harmless, non-functioning tumors that never cause symptoms and don’t need treatment. The real challenge isn’t finding them - it’s figuring out which ones might be dangerous.

What Exactly Is an Adrenal Incidentaloma?

An adrenal incidentaloma is a mass larger than 1 centimeter found by accident during imaging done for another reason. These aren’t symptoms-driven discoveries. You don’t feel it. You don’t know it’s there. It shows up on a CT or MRI ordered for gallstones, kidney stones, or even a car accident. The prevalence jumps with age - 2% in people under 50, but over 7% in those over 70. That’s because older adults get more scans. More scans mean more incidental findings.

The adrenal glands sit on top of each kidney. They make hormones that control blood pressure, metabolism, stress response, and electrolyte balance. When a tumor forms there, it can either sit quietly - or start pumping out too much of one of these hormones. That’s where the risk lies.

Three Types of Adrenal Masses - And What They Mean

Not all adrenal tumors are the same. They fall into three clear groups:

• Functioning tumors - These make extra hormones. Examples include pheochromocytomas (adrenaline), cortisol-producing tumors (Cushing’s syndrome), and aldosterone-secreting tumors (high blood pressure, low potassium).
• Malignant tumors - These are cancerous. Either primary adrenocortical carcinoma (rare, about 2% of incidentalomas) or cancer that spread from elsewhere (like lung or breast cancer).
• Non-functioning benign tumors - The most common type. These are usually adenomas, myelolipomas, or cysts. They don’t make hormones and don’t grow fast. They’re just there.

The goal of evaluation isn’t to remove everything. It’s to find the 20% that need action - and leave the other 80% alone.

Step 1: Rule Out Pheochromocytoma First

Before anything else - even before looking at the scan - you must check for pheochromocytoma. Why? Because if you miss it and operate, you could trigger a deadly surge of adrenaline during surgery. Blood pressure can spike to stroke-levels. Death can happen.

The test? Plasma-free metanephrines or 24-hour urinary fractionated metanephrines. These measure breakdown products of adrenaline and noradrenaline. If they’re high, you don’t go to surgery until you’ve treated the tumor with alpha-blockers for at least 7-14 days. This isn’t optional. It’s life-saving.

Even if you have no symptoms - no headaches, no sweating, no racing heart - you still get tested. About 4% of incidentalomas are pheochromocytomas, and many are silent.

Step 2: Check for Cortisol Overproduction

Next, test for autonomous cortisol secretion - also called subclinical Cushing’s syndrome. This affects 5-10% of incidentalomas. It doesn’t always look like classic Cushing’s (moon face, buffalo hump). Instead, it might just mean high blood pressure, diabetes, or osteoporosis that won’t improve.

The test: a 1-mg dexamethasone suppression test. You take a pill at night. The next morning, you get a blood draw. If your cortisol level is above 1.8 μg/dL (50 nmol/L), it’s suspicious. Above 5.0 μg/dL? That’s a strong signal for surgery, especially if you have metabolic issues.

Newer tests like urinary steroid metabolomics are showing promise - they’re 92% accurate at spotting cortisol excess, better than the dexamethasone test. But they’re not widely available yet.

Step 3: Screen for Aldosterone - Only If You Have High Blood Pressure

If you have high blood pressure, especially if it’s hard to control or you have low potassium, check for primary hyperaldosteronism. This happens in about 4% of incidentalomas.

Test: plasma aldosterone concentration and plasma renin activity. The aldosterone-to-renin ratio tells you if your adrenal is making too much aldosterone. If yes, surgery may be better than lifelong pills.

Step 4: Read the Scan - Size and Shape Matter

A non-contrast CT scan is the first imaging test. It’s cheap, fast, and tells you a lot.

The key number? Hounsfield units (HU). If the tumor has a density below 10 HU, it’s almost certainly a benign adenoma - 70-80% accurate. Fat inside the tumor (seen as dark spots) also points to benign. Myelolipomas have fat. Hematomas have blood.

If the tumor is:

• Over 4 cm - higher chance of cancer
• Over 6 cm - 25% risk of adrenocortical carcinoma
• Irregular edges, uneven texture, or rapid growth - red flags

Growth rate matters. If the tumor grows more than 1 cm per year, or doubles in volume in less than a year, it’s suspicious - even if it’s under 4 cm.

When Is Surgery Necessary?

You need surgery if:

• The tumor is producing hormones (pheochromocytoma, cortisol excess, aldosterone excess)
• The tumor is over 4 cm
• The tumor has imaging features suggesting cancer (irregular shape, high density, necrosis)
• The tumor grows fast - more than 1 cm per year

Size alone isn’t enough. A 5 cm tumor with 8 HU density and normal hormone levels? Probably fine to watch. A 3 cm tumor with 25 HU density and high cortisol? Needs removal.

What About Small, Benign, Non-Functioning Tumors?

If your tumor is under 4 cm, has low Hounsfield units, no hormone excess, and no growth - you’re done. No follow-up scans. No blood tests. No stress.

Some doctors still order yearly scans out of habit. But the guidelines are clear: if it’s clearly benign and not making hormones, no monitoring is needed. You save money, radiation exposure, and anxiety.

Why This Matters - The Human Side

Patients often feel terrified after hearing "tumor." Even if it’s benign, the wait for test results causes real stress. One informal survey of 142 patients found 78% felt high anxiety during evaluation.

The best outcomes come from specialized centers. At places like Columbia’s Adrenal Center, 92% of patients report satisfaction. At general hospitals? Only 68%. Why? Because adrenal work needs a team: endocrinologist, radiologist, surgeon - all experienced.

Most community hospitals don’t have access to plasma metanephrine testing. Only 45% do. And radiologists without adrenal expertise misread scans 15-30% of the time.

The Future: More Precision, Less Guesswork

New tools are coming. Urinary steroid metabolomics is one. It looks at dozens of cortisol breakdown products at once - far more accurate than one blood test. It’s not everywhere yet, but it’s the future.

The Endocrine Society is updating its guidelines in 2024 to reflect new data: surgery for subclinical Cushing’s improves blood sugar, blood pressure, and bone density - especially when cortisol levels are above 5.0 μg/dL.

The big picture? We’re moving from "one-size-fits-all" to personalized risk. A 72-year-old with a 3.5 cm tumor, normal hormones, and diabetes might benefit from surgery. A 50-year-old with the same tumor and no health issues? Probably not.

What to Do If You’re Diagnosed

If you’ve been told you have an adrenal incidentaloma:

1. Don’t panic. Most are harmless.
2. Ask for plasma-free metanephrines and 1-mg dexamethasone suppression test.
3. Get the non-contrast CT scan reviewed by someone who reads adrenal images regularly.
4. If hormone levels are high or the tumor is over 4 cm, ask for a referral to an adrenal specialist.
5. If everything looks normal - ask if you need any follow-up. The answer might be no.

You don’t need to be a doctor to understand this. You just need to ask the right questions.

Common Misconceptions

• "All adrenal tumors need surgery." False. Most don’t.
• "If I have high blood pressure, it’s from the tumor." Maybe. But not always. Test before assuming.
• "I need a yearly scan." Only if the tumor is indeterminate. Otherwise, no.
• "I’ll feel symptoms if it’s dangerous." Pheochromocytomas and cortisol excess can be silent. That’s why testing is mandatory.

Final Thoughts

Adrenal incidentalomas are a product of modern medicine - we see more because we scan more. But seeing more doesn’t mean treating more. The art is knowing when to act - and when to do nothing.

The guidelines are clear. The science is solid. The biggest barrier isn’t medical - it’s awareness. Too many patients get lost in the system, getting unnecessary tests and surgeries because no one connected the dots.

If you’ve been diagnosed, be your own advocate. Ask for the right tests. Ask for a specialist. And remember - not every lump needs to be removed. Sometimes, the best treatment is no treatment at all.