Most adrenal gland tumors are not serious. Roughly 80% are small, benign growths called adenomas that produce no excess hormones and cause no symptoms. These are often discovered by accident during a CT scan or MRI ordered for an unrelated reason, which is why doctors call them “incidentalomas.” Still, about 15% of adrenal tumors do overproduce hormones, and fewer than 5% turn out to be cancerous, so every adrenal mass needs proper evaluation.
Why Most Adrenal Tumors Are Found by Accident
Adrenal tumors rarely announce themselves. The vast majority sit quietly on top of one or both kidneys, producing no symptoms and requiring no treatment. They show up on imaging studies done for back pain, kidney stones, or abdominal complaints. As CT and MRI scans have become more common, so have these incidental findings. The discovery can feel alarming, but the overwhelming odds favor a harmless growth.
Doctors evaluate an adrenal mass based on two key questions: Is it making excess hormones? And does it look suspicious for cancer on imaging? The answers determine whether you need monitoring, blood work, or surgery.
How Doctors Tell Benign From Dangerous
On a CT scan, the density of an adrenal mass is measured in Hounsfield units. Benign adenomas are typically rich in fat, which makes them appear less dense. A reading of 10 Hounsfield units or below, combined with smooth borders and a size under 4 centimeters, strongly suggests a harmless adenoma. That combination has a specificity above 93% for identifying benign growths, meaning false alarms are rare.
Size matters. Most endocrine societies consider 4 centimeters the threshold where malignancy risk rises enough to recommend surgery for a nonfunctioning tumor. The National Institutes of Health classifies tumors under 4 cm as low risk, 4 to 6 cm as indeterminate, and above 6 cm as high risk. Any tumor that produces excess hormones is a candidate for removal regardless of size.
Hormone-Producing Tumors
About 15% of adrenal tumors actively secrete hormones, and the type of hormone determines the symptoms and health consequences. Even some tumors labeled “nonfunctional” on standard testing may release low levels of stress hormones that slightly raise the risk of diabetes and cardiovascular problems over time.
Excess Cortisol (Cushing’s Syndrome)
An estimated 10% of adrenal tumors overproduce cortisol, the body’s main stress hormone. When cortisol stays elevated for months or years, the effects are widespread: weight gain concentrated in the face, neck, and trunk while arms and legs stay thin; wide purple stretch marks on the abdomen and hips; easy bruising; muscle weakness; and high blood sugar. Women may notice irregular periods and excess facial hair. Men may experience reduced sex drive and fertility problems. Children with the condition tend to gain weight while growing more slowly than their peers.
Some cortisol-producing tumors cause a milder, “subclinical” version without the classic physical changes, but they can still drive up blood pressure and blood sugar quietly over time.
Excess Adrenaline (Pheochromocytoma)
Pheochromocytomas arise from the inner part of the adrenal gland and flood the body with adrenaline and related hormones. The hallmark symptoms are episodes of severe headaches, rapid heartbeat, and drenching sweats, often accompanied by dangerously high blood pressure. These episodes can be triggered by physical activity, stress, or certain foods.
Pheochromocytomas were traditionally called “the 10% tumor” because about 10% were thought to be hereditary, 10% occurred outside the adrenal glands, and 10% were malignant. Updated research has revised the hereditary figure upward: roughly 25% of patients with an apparently sporadic pheochromocytoma carry a genetic variant linked to the disease. That means genetic testing is now recommended for most people diagnosed with one.
Excess Aldosterone (Conn’s Syndrome)
Some adrenal tumors overproduce aldosterone, a hormone that controls salt and potassium balance. The result is high blood pressure that resists standard medications, combined with low potassium levels that can cause muscle cramps, weakness, and fatigue. Conn’s syndrome is one of the most common curable causes of high blood pressure. Screening involves a blood test measuring the ratio of aldosterone to renin, and removing the tumor or treating with targeted medication often normalizes blood pressure.
When an Adrenal Tumor Is Cancer
Primary adrenal cancer, called adrenocortical carcinoma, is rare. It accounts for fewer than 5% of adrenal masses. These tumors tend to be large at diagnosis, often exceeding 6 centimeters, and they may produce hormones that cause rapid, noticeable changes in the body.
Survival depends heavily on how far the cancer has spread at the time of diagnosis. Based on data from 2015 to 2021 compiled by the American Cancer Society, the five-year relative survival rate is 80% when the cancer is confined to the adrenal gland, 62% when it has spread to nearby tissues or lymph nodes, and 39% when it has reached distant organs. The overall five-year survival rate across all stages is 57%.
More commonly, a malignant adrenal mass is not a primary adrenal cancer but a metastasis from somewhere else. Lung cancer accounts for about 39% of adrenal metastases and breast cancer about 35%, with melanoma, gastrointestinal cancers, and kidney cancers making up much of the rest. When a patient with a known cancer history has an adrenal mass, doctors evaluate it differently than an isolated finding in an otherwise healthy person.
Treatment and Recovery
Small, nonfunctioning adrenal tumors under 4 cm with benign imaging features typically require no treatment at all. Your doctor may recommend a follow-up scan in 6 to 12 months to confirm the mass hasn’t grown, along with blood or urine tests to check for hormone overproduction.
Surgery is recommended for tumors that produce excess hormones, tumors 4 centimeters or larger with concerning imaging features, or any mass that grows significantly on follow-up. Most adrenal surgery is now done laparoscopically or with robotic assistance through small incisions. Recovery from minimally invasive surgery is quick: many patients go home the same day and return to normal activities within one to two weeks. Open surgery, reserved for larger or more complex tumors, may require up to five days in the hospital and a longer recovery period, though most people are back to their routine within two to three weeks.
If the removed tumor was producing cortisol, you may need temporary hormone replacement afterward because the opposite adrenal gland can take weeks or months to “wake up” and resume normal production. Your endocrinologist will taper the replacement as your body adjusts.
What Determines How Serious Your Tumor Is
Three factors drive the answer. Size is the first: tumors under 4 cm with low density on CT are almost always benign. Hormone activity is the second: even a small tumor causing Cushing’s syndrome or dangerous blood pressure spikes needs attention. And imaging characteristics are the third: irregular borders, high density, and rapid growth on follow-up scans all raise concern for malignancy.
For the large majority of people who find out they have an adrenal mass, the news is reassuring after appropriate workup. A single round of blood tests and a careful review of the imaging is often enough to confirm the tumor is benign and nonfunctional, requiring nothing more than periodic monitoring.