An adrenal mass is any growth found in or on one of the two adrenal glands, the small hormone-producing organs that sit on top of each kidney. The vast majority are benign, non-functioning adenomas discovered by accident when a CT or MRI is done for an unrelated reason. In large imaging studies, adrenal abnormalities show up on roughly 1 to 13 percent of abdominal scans, depending on the population being scanned and how closely radiologists look.1PubMed Central. An Adrenal Incidentaloma: How Often Is It Detected and What Are the Consequences?2Journal of the Endocrine Society. Adrenal Incidentaloma: Prevalence and Referral Patterns From Routine Practice in a Large UK University Teaching Hospital Whether that growth demands urgent attention or just periodic monitoring depends on two questions: is it making hormones it shouldn’t be, and does it look like it could be cancer?
Why Most Adrenal Masses Are Found by Accident
Doctors use the term “adrenal incidentaloma” for a mass discovered on imaging that was ordered for something else entirely, such as investigating back pain, kidney stones, or abdominal symptoms. These incidentalomas are extremely common. A five-year review of nearly half a million CT and MRI scans at a large UK hospital found adrenal incidentalomas in about 1.2 percent of all scans, rising to over 3 percent for abdominal CT specifically.2Journal of the Endocrine Society. Adrenal Incidentaloma: Prevalence and Referral Patterns From Routine Practice in a Large UK University Teaching Hospital In populations already being scanned for cancer, the rate climbs higher: one study at a comprehensive cancer center found adrenal abnormalities on over 13 percent of abdominal CTs.3Frontiers in Endocrinology. The prevalence and spectrum of reported incidental adrenal abnormalities in abdominal computed tomography of cancer patients
The rising use of cross-sectional imaging over the past few decades means more of these growths are being found than ever before. Most people who have one will never experience symptoms from it. The challenge for doctors is figuring out which of these incidental findings need treatment and which can be safely left alone.
The Most Common Benign Types
The single most common adrenal mass is an adenoma, a non-cancerous growth of the adrenal cortex (the gland’s outer layer). Most adenomas are small, do not produce excess hormones, and never cause problems. They can, however, reach unusual sizes. The largest benign adrenal adenoma ever reported in the literature measured 32 centimeters across and weighed over 7 kilograms, though cases that extreme are vanishingly rare.4PubMed Central. Giant non-functional adrenal adenoma: A case report A two-year follow-up study of 32 people with non-functioning benign adrenal incidentalomas found no malignant transformation during that period, though one patient did develop subtle excess cortisol secretion by the end of the first year.5PubMed. Two-year follow-up of thirty-two non-functional benign adrenal incidentalomas
Another distinctive benign type is the myelolipoma, a growth made of mature fat tissue mixed with blood-forming cells similar to what you’d find in bone marrow. Myelolipomas are easy to identify on imaging because fat has a characteristic negative density value on CT scans, making them look obviously different from other adrenal masses.6PubMed Central. Myelolipomas and other fatty tumours of the adrenals They are benign and generally do not need surgery unless they grow large enough to cause discomfort or bleeding.7PubMed Central. Adrenal myelolipoma: Controversies in its management
Other benign possibilities include adrenal cysts (fluid-filled sacs), ganglioneuromas (nerve-tissue tumors), and simple hyperplasia (thickening of adrenal tissue). The type matters less than the two key clinical questions: is the mass hormonally active, and does it have features suggesting malignancy?
When a “Silent” Mass Is Quietly Making Hormones
Some adrenal masses produce excess hormones without causing the dramatic symptoms doctors are trained to recognize. This is the category that catches people off guard. The most common scenario is mild cortisol overproduction, sometimes called subclinical hypercortisolism. Unlike full-blown Cushing’s syndrome, which causes a distinctive round face, purple stretch marks, and rapid weight gain, subclinical cortisol excess shows up as garden-variety health problems: hard-to-control blood pressure, rising blood sugar, weight creeping up around the midsection.8PubMed Central. Subclinical Hypercortisolism: An Important, Unrecognized Dysfunction
A study of 50 patients with adrenal incidentalomas and subtle cortisol excess found that about half had mild-to-severe high blood pressure, a quarter had type 2 diabetes, and more than a third were obese.9The Journal of Clinical Endocrinology & Metabolism. Subclinical Cushing’s Syndrome in Patients with Adrenal Incidentaloma: Clinical and Biochemical Features Taken individually, those conditions are ordinary. But when they cluster around a person with an adrenal mass, the mass may be the hidden driver. Another study compared people with subclinical cortisol-producing adenomas to matched controls and found strikingly worse cardiovascular profiles in the adenoma group: higher blood pressure, worse cholesterol, more insulin resistance, and thicker carotid artery walls, a marker of early atherosclerosis.10The Journal of Clinical Endocrinology & Metabolism. Patients with Subclinical Cushing’s Syndrome due to Adrenal Adenoma Have Increased Cardiovascular Risk Among those 28 patients, over 60 percent had high blood pressure and over 70 percent had abnormal blood fats. Only four patients in the entire group had no cardiovascular risk factors at all. Removing the adrenal gland in patients with this kind of excess has been shown to reduce the need for blood pressure medications over time.11PubMed Central. Impact of Adrenalectomy on Morbidity in Patients with Non-Functioning Adrenal Cortical Tumours, Mild Hypercortisolism and Cushing’s Syndrome as Assessed by National and Quality Registries
Less common but more dramatic is pheochromocytoma, a tumor of the adrenal medulla (the gland’s inner core) that pumps out adrenaline-type hormones called catecholamines. Classic symptoms include sudden episodes of pounding heart, profuse sweating, severe headaches, and dangerous blood pressure spikes.12PubMed. Pheochromocytomas and Hypertension A pheochromocytoma can be lethal if undiagnosed, but it is almost always curable with surgery.13PubMed. Adrenal causes of hypertension: pheochromocytoma and primary aldosteronism Critically, doctors must test for pheochromocytoma before any surgical procedure on an adrenal mass, because manipulating the tumor without proper medication preparation can trigger a life-threatening blood pressure crisis.14PubMed Central. Hypertension in pheochromocytoma: characteristics and treatment
Some adrenal masses overproduce aldosterone, a hormone that regulates salt and water balance, leading to resistant high blood pressure that doesn’t respond well to standard medications.15PubMed Central. Resistant hypertension with adrenal nodule: are we removing the right gland? Rarer still are masses that produce sex hormones. Androgen-secreting adenomas can cause rapid body hair growth and other masculinizing changes in women.16PubMed Central. A rare case of pure testosterone-secreting adrenal adenoma in a postmenopausal elderly woman Estrogen-secreting adrenal tumors, which are extremely rare, can cause breast tissue growth in men and abnormal bleeding in women.17PubMed Central. Feminizing adrenocortical tumors: Literature review
How Doctors Tell Benign From Dangerous
When an adrenal mass appears on imaging, clinicians look at a few key features to decide how worried to be. The first and simplest is size. Most guidelines treat 4 centimeters (roughly an inch and a half) as the threshold above which surgery should at least be strongly considered, because the probability of malignancy rises with size.18PubMed Central. Adrenal Incidentaloma Controversial Size Recommendations In one surgical series, using 4 centimeters as the cut-off would have caught all primary malignant adrenal tumors while reducing unnecessary operations on benign masses.19PubMed. Revisiting adrenal mass size as an indication for adrenalectomy
Imaging density on CT scan provides another strong clue. Benign adenomas tend to be rich in fat at the cellular level, which makes them appear less dense on CT. Radiologists measure this density in Hounsfield units. A mass measuring 10 or below on an unenhanced CT is almost certainly a benign adenoma. In one study, every mass at or below that threshold turned out to be an adenoma, giving a 100 percent positive predictive value at that cut-off.20Surgery. Radiologic characterization of adrenal masses: The role of computed tomography—derived attenuation values Non-adenomas averaged much higher density values.
MRI adds another tool through a technique called chemical-shift imaging, which detects the microscopic fat within adenoma cells. One study found that a specific signal intensity index could distinguish adenomas from metastatic tumors with no overlap between the two groups.21PubMed. Characterization of adrenal tumors by chemical shift fast low-angle shot MR imaging: comparison of four methods of quantitative evaluation Another study using this approach reported a mean positive predictive value of 95 percent for identifying a benign mass, jumping to 99 percent when the radiologists were most confident in their reading.22PubMed. Distinction between benign and malignant adrenal masses: value of T1-weighted chemical-shift MR imaging
When CT and MRI leave the diagnosis uncertain, PET scanning can help. This imaging technique measures metabolic activity: cancers tend to be far more metabolically active than benign adenomas. A study evaluating PET scans in people without a known cancer found that malignant adrenal masses had median metabolic activity ratios several times higher than benign ones. Using a specific cut-off, the test achieved about 85 percent sensitivity and 90 percent specificity for distinguishing benign from malignant masses.23PubMed Central. 18 F-FDG-PET/CT Evaluation of Indeterminate Adrenal Masses in Noncancer Patients An earlier study reported even higher numbers for PET accuracy, though these figures tend to vary with the population studied and the scanning protocol used.24Journal of Nuclear Medicine. 18F-FDG PET in Characterizing Adrenal Lesions Detected on CT or MRI
Alongside imaging, every patient with a newly found adrenal mass should have bloodwork to check for hormone overproduction. Guidelines call for testing catecholamine levels (to rule out pheochromocytoma) in all patients, with additional testing for excess cortisol and aldosterone depending on symptoms and blood pressure.25The Journal of Clinical Endocrinology & Metabolism. Approach to the Patient with an Adrenal Incidentaloma
When an Adrenal Mass Is Cancer
There are two paths to a malignant adrenal mass: cancer that starts in the adrenal gland itself, or cancer that has spread there from somewhere else. The first type, adrenocortical carcinoma, is rare but aggressive. At the time of diagnosis, these tumors tend to be large, with an average diameter over 10 centimeters, and they often have irregular borders and areas of internal bleeding or dead tissue visible on CT.26PubMed. Management of adrenocortical carcinoma One hallmark is invasion into surrounding structures, sometimes extending into the major vein that carries blood back to the heart.27PubMed Central. Adrenocortical carcinoma: a literature review Survival depends heavily on the stage at which it is caught: five-year survival ranges from roughly 60 to 80 percent for tumors confined to the gland, down to 10 to 20 percent for disease that has already spread to distant sites.28The Lancet Diabetes & Endocrinology. Management of adrenocortical carcinoma Only one drug, mitotane, is specifically approved for adrenocortical carcinoma, which gives some sense of how limited the treatment options remain.
The second scenario, metastatic disease, is actually more common than primary adrenal cancer. The adrenal glands are a frequent landing spot for cancers originating elsewhere. In one large autopsy and surgical study, the most common primaries metastasizing to the adrenal gland were kidney cancer, lung cancer, bladder cancer, and liver cancer.29Pathology – Research and Practice. Metastatic diseases to the adrenal gland: A comprehensive study from an academic institution with emphasis on clinical occult cases In a separate analysis of metastatic patterns across cancers, about half of all adrenal metastases originated from lung cancer.30PubMed. Metastatic patterns in adenocarcinoma For someone with a known cancer history, a new adrenal mass raises different questions than it would in someone with no cancer history, and the workup may include biopsy to confirm or rule out metastatic disease.
The Role of Biopsy
Image-guided needle biopsy of an adrenal mass has a specific, narrow role. It is most useful when a patient has a known cancer and the question is whether a new adrenal mass is a metastasis or just an incidental adenoma. In that context, biopsy can confirm the nature of the deposit and guide treatment decisions.31PubMed. Changing role of imaging-guided percutaneous biopsy of adrenal masses: evaluation of 50 adrenal biopsies
For masses without a known primary cancer, biopsy is less helpful and sometimes risky. In one decade-long review, needle biopsy detected adrenocortical carcinoma only half the time it was actually present, with three of six cases missed on biopsy.32JAMA Surgery. Limited Value of Adrenal Biopsy in the Evaluation of Adrenal Neoplasm: A Decade of Experience Pheochromocytoma must always be ruled out biochemically before biopsy, because puncturing a catecholamine-producing tumor can be dangerous. For most masses that look suspicious on imaging but don’t have a known primary cancer to match, surgery rather than biopsy is the preferred approach.
Watch, Operate, or Ignore
Guidelines generally recommend surgery for adrenal masses larger than 4 centimeters that lack clear benign imaging features, for any mass with confirmed hormone overproduction that is causing clinical harm, and for any mass with imaging characteristics that suggest malignancy regardless of size.33The Journal of Clinical Endocrinology & Metabolism. Medical and Surgical Evaluation and Treatment of Adrenal Incidentalomas The 4-centimeter rule is not absolute: some groups use slightly different thresholds, and decision-making often weighs imaging appearance and hormonal status alongside size.18PubMed Central. Adrenal Incidentaloma Controversial Size Recommendations
For small, clearly benign-looking, hormonally inactive masses under 4 centimeters, recent European and Korean guidelines suggest that repeat imaging may not even be necessary as long as no new symptoms develop. This is a shift from older recommendations, which called for follow-up CT scans at 3 to 12 months for nearly everyone with an incidentaloma.34Endocrinology and Metabolism. Is Follow-up of Adrenal Incidentalomas Always Mandatory? The updated thinking reflects the fact that small, low-density adrenal adenomas very rarely change character over time. Hormonal re-testing is also not needed on a schedule unless new clinical signs appear, such as worsening blood pressure, new glucose problems, or unexplained weight gain.
If surgery is needed, the standard approach today is minimally invasive. A systematic review and meta-analysis comparing open, conventional laparoscopic, retroperitoneoscopic (going through the back), and robotic adrenalectomy found that complication rates were similar across all techniques. The minimally invasive options offered less blood loss and shorter hospital stays, with the retroperitoneoscopic and robotic approaches leading to the shortest recoveries.35PubMed. Evaluation of Open and Minimally Invasive Adrenalectomy: A Systematic Review and Network Meta-analysis A more recent analysis of randomized trials found that the posterior retroperitoneoscopic approach had the shortest operating time, lowest pain scores, shortest hospital stays, and lowest cost per case.36PubMed Central. Comparing surgical outcomes of approaches to adrenalectomy – a systematic review and network meta-analysis of randomised clinical trials Open surgery is generally reserved for very large tumors or suspected cancers where wide margins are needed.
Hereditary Syndromes That Raise the Risk
Most adrenal masses occur sporadically with no family connection. But a subset are linked to inherited genetic syndromes, and recognizing these matters because it changes screening for the patient and their relatives. Adrenocortical carcinoma is associated with Li-Fraumeni syndrome, caused by mutations in the TP53 gene, a master tumor-suppressor gene whose dysfunction predisposes people to a wide range of cancers throughout life.37PubMed Central. Current prospects of hereditary adrenal tumors: towards better clinical management Pheochromocytoma has an even broader genetic landscape: multiple genes including those involved in a family of enzymes called succinate dehydrogenase, as well as the RET, NF1, and VHL genes, can predispose someone to these catecholamine-producing tumors. Because the list of potential driver genes is long, guidelines increasingly recommend comprehensive genetic panel testing for all patients diagnosed with pheochromocytoma or a closely related tumor called paraganglioma.37PubMed Central. Current prospects of hereditary adrenal tumors: towards better clinical management
In children, adrenal tumors are uncommon but disproportionately associated with genetic changes. Researchers have identified mutations in several genes, including TP53 and IGF2, as contributors to childhood adrenal tumor development.38PubMed Central. Adrenocortical tumors and hyperplasias in childhood–etiology, genetics, clinical presentation and therapy An adrenal mass in a child warrants a more aggressive diagnostic approach than the same finding in a middle-aged adult, both because the baseline likelihood of malignancy is higher relative to the low overall incidence and because a hereditary syndrome may be at play.
Living With an Adrenal Incidentaloma
For the many people who are told they have an adrenal mass after a routine scan, the experience often generates anxiety out of proportion to the actual risk. The word “mass” sounds alarming, but in practice the vast majority of these findings are small, benign adenomas that will never grow, never produce hormones, and never require treatment. The evidence suggests that benign, non-functioning adrenal masses under 4 centimeters have an extremely low rate of conversion to anything harmful over years of follow-up.5PubMed. Two-year follow-up of thirty-two non-functional benign adrenal incidentalomas
The practical question most patients ask is: do I need repeat scans forever? Current thinking is moving toward a less is more approach for masses that clearly look benign. If the mass measures under 4 centimeters, has a low CT density consistent with an adenoma, and initial hormone testing is normal, many experts now say no routine follow-up imaging is needed. What matters more is paying attention to your body: new or worsening high blood pressure, unexplained weight gain, episodes of sweating with a racing heart, or changes in blood sugar are all reasons to revisit the question with your doctor. In the absence of new symptoms, the finding itself can often be filed away rather than anxiously re-investigated on a set schedule.