An adrenal tumor is a growth that forms in one or both of your adrenal glands, the small hormone-producing organs that sit on top of each kidney. Most adrenal tumors are benign (noncancerous) and never cause symptoms. They’re so common that about 5% of people who get a CT scan for an unrelated reason turn out to have one, often without ever knowing it was there. These surprise findings are called adrenal incidentalomas, and in most cases they require nothing more than monitoring.
That said, some adrenal tumors do produce excess hormones or, rarely, turn out to be cancerous. Understanding the difference matters for knowing what to watch for and what comes next.
What Your Adrenal Glands Do
Each adrenal gland has two distinct parts that produce different hormones. The outer layer, called the cortex, makes three types: cortisol (which regulates metabolism, blood sugar, inflammation, and your sleep-wake cycle), aldosterone (which controls blood pressure and the balance of sodium and potassium in your blood), and weak sex hormones that get converted into estrogen or testosterone elsewhere in the body. The inner core, called the medulla, produces adrenaline and noradrenaline, the “fight or flight” hormones that spike your heart rate, send blood to your muscles, and sharpen your focus during stress.
A tumor can form in either part of the gland, and its location largely determines what kind of trouble it can cause.
Benign vs. Cancerous Adrenal Tumors
The vast majority of adrenal tumors are adenomas, which are small, benign growths. They tend to be well-defined, stable in size, and if they produce hormones at all, they typically make only one type. Many produce no excess hormones whatsoever and are only discovered by accident on imaging.
Adrenocortical carcinoma (ACC) is the cancerous form, and it’s rare. These tumors are usually large at the time of diagnosis, averaging about 9 centimeters across, and roughly 70% are bigger than 6 centimeters. On a scan, they often look uneven and may contain areas of dead tissue, bleeding, or calcium deposits. One hallmark that raises suspicion for cancer: producing multiple types of hormones at once, particularly cortisol combined with male sex hormones.
Size is one of the simplest clues doctors use to tell these apart. A tumor under 4 centimeters that looks smooth and uniform on a scan is overwhelmingly likely to be benign. Once a tumor exceeds 4 centimeters, surgical evaluation becomes a more serious consideration.
Functional vs. Nonfunctional Tumors
Adrenal tumors fall into two broad categories based on whether they pump out extra hormones. A “functional” tumor overproduces one or more hormones and causes noticeable symptoms. A “nonfunctional” tumor sits quietly, producing either normal hormone levels or none at all. Nonfunctional tumors make up the majority of incidental findings and are typically monitored with periodic imaging to make sure they aren’t growing.
Functional tumors, while less common, tend to get diagnosed because of the symptoms they cause. The three main types correspond to the hormones they overproduce.
Cortisol-Producing Tumors and Cushing’s Syndrome
When a tumor churns out too much cortisol, the result is Cushing’s syndrome. Because cortisol touches nearly every system in the body, the effects are widespread and often visible. People with persistently high cortisol levels develop a recognizable pattern: weight gain concentrated in the face, neck, and trunk while the arms and legs stay thin or even lose muscle. A round “moon face,” a fatty hump between the shoulders, and increased fat around the base of the neck are classic signs.
Skin changes are also telling. Wide purple stretch marks may appear on the abdomen, breasts, hips, and underarms. Bruising happens easily, and muscles feel weak. Over time, high cortisol raises blood sugar, thins bones, and disrupts sleep. These changes tend to develop gradually, which means people sometimes live with them for months or years before the underlying cause is identified.
Aldosterone-Producing Tumors and Conn’s Syndrome
A tumor that overproduces aldosterone causes a condition called primary aldosteronism, or Conn’s syndrome. Its two defining features are high blood pressure and low potassium. Because aldosterone tells the kidneys to hold onto sodium and water while flushing out potassium, excess production drives blood pressure up and depletes a mineral your muscles and heart need to function properly.
Low potassium can cause muscle cramps, weakness, fatigue, and in more severe cases, abnormal heart rhythms. The high blood pressure from Conn’s syndrome is often resistant to standard medications, which is sometimes the clue that leads doctors to investigate the adrenal glands. Left untreated, the sustained blood pressure elevation increases the risk of heart disease, stroke, and kidney damage.
Pheochromocytomas and Adrenaline Surges
Pheochromocytomas are rare tumors that grow in the adrenal medulla and release bursts of adrenaline and noradrenaline. The hallmark is episodes of sudden, severe high blood pressure, often accompanied by a pounding heartbeat, intense headaches, and sweating. These episodes can be triggered by physical exertion, stress, certain medications, or even anesthesia, and they can feel alarming because they mimic a panic attack or heart emergency.
High blood pressure is the most common complication. In extreme cases, a massive adrenaline surge can trigger dangerous heart rhythm problems or a hypertensive crisis severe enough to affect the brain, causing confusion, neurological symptoms, or seizures. Because these events can be life-threatening, pheochromocytomas are almost always treated with surgical removal once identified.
How Adrenal Tumors Are Found
Most adrenal tumors are discovered incidentally during a CT or MRI scan ordered for something else entirely, like back pain, kidney stones, or a car accident evaluation. Once a mass shows up on imaging, doctors need to answer two questions: Is it making excess hormones? And is it cancerous?
The imaging itself provides early clues. On a CT scan, benign adenomas tend to have a low density because they contain more fat. A mass that measures at or below a specific density threshold is very likely a benign, fat-rich adenoma, with about 98% certainty. If the initial scan is less clear, a follow-up scan with contrast dye can help. Benign adenomas wash out the dye quickly, while malignant tumors tend to hold onto it, and this technique pushes diagnostic accuracy to around 96%.
For the hormone question, blood and urine tests check for overproduction. These typically include cortisol levels (often through an overnight suppression test or a 24-hour urine collection), aldosterone-to-renin ratios to screen for Conn’s syndrome, and measurements of adrenaline byproducts called metanephrines in either blood or a 24-hour urine sample to rule out pheochromocytoma. These tests are standard even when a tumor looks harmless on a scan, because a small, benign-looking growth can still be quietly overproducing hormones.
Treatment and Monitoring
What happens next depends entirely on whether the tumor is functional, how large it is, and whether cancer is suspected. Small, nonfunctional tumors under 4 centimeters that look benign on imaging are typically watched over time. Repeat scans at 6 to 12 months, and sometimes again at 24 months, check for growth. Hormone testing may also be repeated to catch any change in function.
Surgery to remove the affected adrenal gland is recommended for tumors that are functional (causing hormone-related symptoms), larger than 4 centimeters, or suspicious for cancer. Most of these surgeries are done laparoscopically through small incisions, which means shorter hospital stays and faster recovery compared to open surgery. People generally do well with one functioning adrenal gland, since the remaining gland compensates fully.
For pheochromocytomas, preparation before surgery is critical. Patients take medication for several weeks beforehand to block the effects of excess adrenaline and stabilize blood pressure, reducing the risk of a dangerous surge during the operation. For cortisol-producing tumors, the opposite adrenal gland may have “gone to sleep” because the tumor was doing all the work. After surgery, temporary hormone replacement is often needed until the remaining gland wakes back up, which can take weeks to months.
Adrenocortical carcinoma, when confirmed, typically requires open surgery to remove the tumor along with surrounding tissue. Outcomes depend heavily on the stage at diagnosis, which is one reason larger or rapidly growing adrenal masses get expedited surgical evaluation rather than a wait-and-watch approach.