An adrenal tumor is any abnormal growth in one or both of the adrenal glands, the small hormone-producing organs that sit on top of each kidney. Most are benign, discovered by accident on imaging done for something else, and never cause symptoms. But some produce excess hormones that quietly damage the cardiovascular system, and a small fraction are cancerous. The distinction between a harmless lump and a dangerous one depends on two questions: is it making hormones it shouldn’t be, and is it malignant?
Why Most Adrenal Tumors Are Found by Accident
The term “adrenal incidentaloma” refers to any adrenal mass discovered on imaging performed for an unrelated reason, like a CT scan after a car accident or an abdominal scan investigating kidney stones. These incidental findings are common. Because modern imaging is so detailed and so frequently ordered, doctors find adrenal masses in a sizable percentage of abdominal scans, particularly in older adults. Most of these turn out to be small, non-functioning benign adenomas that require nothing more than follow-up.
The challenge is that a small but meaningful fraction of incidentalomas are either hormonally active or malignant. Current guidelines recommend that every incidentally found adrenal mass get a thorough workup to rule out both possibilities. That means hormonal blood and urine tests alongside imaging characteristics like size and density on CT.1PubMed. Diagnosis, Management, and Follow-Up of the Incidentally Discovered Adrenal Mass: CUA Guideline Endorsed by the AUA The evaluation typically involves endocrinologists, radiologists, and sometimes urologists working together.
Functional Versus Non-Functional Tumors
The single most important distinction in adrenal tumors is whether they produce excess hormones. A “functional” tumor churns out hormones the body doesn’t need, creating symptoms and health consequences even if the tumor itself is tiny and benign. A “non-functional” tumor sits there quietly, producing either nothing extra or amounts too small to matter clinically. Roughly 60% of adrenocortical tumors are functional, meaning most adrenal tumors that arise from the outer layer of the gland are doing something hormonally.2PubMed Central. A case of androgen-secreting adrenal carcinoma with non-classical congenital adrenal hyperplasia
The type of hormone a functional tumor produces determines which symptoms appear. Because the adrenal glands manufacture several different hormones, including cortisol, aldosterone, adrenaline, and sex steroids like testosterone, the symptom picture varies dramatically depending on which hormone is overproduced. Two people with adrenal tumors can look like they have completely different diseases.
Cortisol-Producing Tumors and Cushing’s Syndrome
When a benign adrenal adenoma pumps out excess cortisol on its own, without the usual signal from the pituitary gland, the result is Cushing’s syndrome. Cortisol is the body’s main stress hormone, involved in blood sugar regulation, immune function, and fat storage. Chronically elevated cortisol reshapes the body in distinctive ways: fat accumulates on the face, neck, and trunk while arms and legs stay thin; the skin becomes fragile and bruises easily; reddish-purple stretch marks appear on the abdomen; muscles weaken; and bones thin. High blood pressure, elevated blood sugar, and mood changes round out the picture.3PubMed Central. Cushing’s syndrome: from physiological principles to diagnosis and clinical care
Not every cortisol-producing adrenal tumor causes the full-blown syndrome, though. A condition called mild autonomous cortisol secretion (MACS) affects up to about a third of people with adrenal incidentalomas. These tumors release modestly elevated cortisol, not enough to cause the dramatic fat redistribution or purple stretch marks, but enough to quietly raise cardiovascular risk.4PubMed. Cardiovascular complications of mild autonomous cortisol secretion People with MACS show higher rates of high blood pressure, abnormal blood sugar, unhealthy cholesterol levels, and obesity compared to people whose adrenal tumors are truly non-functional.5PubMed. Cardiometabolic risk and therapeutic outcomes in mild autonomous cortisol secretion This is one reason why the “harmless lump found by accident” narrative can be misleading. Even when a tumor looks benign and the patient feels fine, subclinical hormone excess can be doing real damage over years.
Aldosterone-Producing Tumors
An aldosterone-producing adenoma, sometimes called a Conn’s adenoma, overproduces aldosterone, the hormone that controls sodium and potassium balance. The classic presentation is high blood pressure that resists the usual medications, combined with low potassium levels, excessive potassium loss in the urine, and a shift in blood chemistry toward alkalosis.6Arquivos Brasileiros de Cardiologia. Conn’s adenoma: a cause of hypertension and hypokalemia The low potassium can cause muscle cramps, weakness, and heart palpitations.
What makes aldosterone-producing tumors especially worth knowing about is that they represent a surgically curable form of high blood pressure. If the excess aldosterone is coming from one adrenal gland rather than both, removing that gland can resolve or dramatically improve the hypertension. The tricky part is confirming that the overproduction is one-sided. Adrenal vein sampling, a procedure in which a radiologist threads a catheter into the veins draining each adrenal gland and measures aldosterone levels on each side, is considered the most reliable way to make that determination.7PubMed Central. Adrenal vein sampling: technique and protocol, a systematic review Despite being recommended by guidelines, adrenal vein sampling remains underused, meaning some patients with curable hypertension never get diagnosed properly.8PubMed. An expert consensus statement on use of adrenal vein sampling for the subtyping of primary aldosteronism
Pheochromocytoma
Pheochromocytomas arise not from the outer cortex of the adrenal gland but from the inner medulla, the part responsible for making adrenaline (epinephrine) and noradrenaline (norepinephrine). These tumors release surges of catecholamines, the fight-or-flight hormones, producing episodes of severe high blood pressure, pounding heartbeat, drenching sweats, headache, and intense anxiety. The episodes can be triggered by physical exertion, certain foods, or even abdominal pressure, but they can also strike without warning.9PubMed Central. Hypertension in pheochromocytoma: characteristics and treatment
Left untreated, the extreme blood pressure spikes from a pheochromocytoma can damage the heart, cause strokes, or be fatal. This is one adrenal tumor where delays in diagnosis carry serious consequences. Diagnosis involves measuring catecholamine breakdown products in the blood or urine, followed by imaging to locate the tumor. Some pheochromocytomas occur outside the adrenal gland altogether, in clusters of similar tissue along the spine called paraganglia. Those are called paragangliomas and behave similarly.
Sex Hormone-Producing Tumors
Some adrenal tumors overproduce androgens (like testosterone) or, far more rarely, estrogens. In women, an androgen-producing tumor can cause rapid-onset excess hair growth on the face and body, acne, deepening of the voice, and menstrual irregularity. One study found that all women with virilizing adrenal tumors had elevated blood levels of testosterone or DHEA-S, though elevated levels of those hormones alone don’t prove a tumor is present, since about half of women with non-cancerous excess hair growth also show elevated levels of at least one of those markers.10PubMed. Identification of virilizing adrenal tumors in hirsute women
Androgen-secreting adrenal cancers are extremely rare, and estrogen-secreting adrenal cancers are rarer still.11PubMed. Androgen- and estrogen-secreting adrenal cancers In men, an estrogen-secreting adrenal tumor can cause breast enlargement and other feminizing changes. The diagnostic challenge with these tumors is that the hormonal patterns and imaging appearance of benign and malignant sex-steroid-producing tumors overlap considerably, making it hard to tell cancer from a non-cancerous adenoma before surgery.
Adrenocortical Carcinoma
Adrenocortical carcinoma (ACC) is the main malignant tumor arising from the adrenal cortex itself. It is rare, with an estimated incidence of less than two cases per million people per year in the United States, but it is aggressive.12PubMed. Adrenocortical carcinoma: Diagnosis, prognostic classification and treatment of localized and advanced disease ACC can be functional, producing cortisol, aldosterone, or sex steroids, or non-functional. When it is functional, the hormonal symptoms described above can actually serve as an early alert, drawing medical attention before the cancer has spread widely. Non-functional ACC tends to be caught later, often only when the tumor grows large enough to cause pain or is found incidentally.
Stage at diagnosis matters enormously. Patients with stage I through III disease who undergo surgical removal have a median survival measured in years, whereas those with stage IV (metastatic) disease who do not receive surgery have a median survival of only about six months.13The Journal of Clinical Endocrinology & Metabolism. Predictors of Survival in Adrenocortical Carcinoma: An Analysis From the National Cancer Database The five-year survival rate for metastatic ACC is below 15%.12PubMed. Adrenocortical carcinoma: Diagnosis, prognostic classification and treatment of localized and advanced disease Median age at diagnosis is around 55, with no major difference by sex.
When the Adrenal Gland Hosts Cancer from Elsewhere
Not every malignant mass in the adrenal gland started there. The adrenal glands are a common destination for metastases from cancers originating in other organs. In a large surgical series, the most common primary cancers that spread to the adrenal glands were lung cancer (accounting for nearly half of cases), followed by kidney cancer, melanoma, sarcoma, and colorectal cancer.14Annals of Surgery. Adrenalectomy for Secondary Malignancy: Patients, Outcomes, and Indications Distinguishing a metastasis from a primary adrenal tumor matters because it changes the treatment approach entirely. Imaging characteristics help: metastases tend to have higher density on unenhanced CT scans compared to benign adenomas, which are usually fat-rich and low-density.15PubMed. Characterization of adrenal adenomas and metastases: correlation between unenhanced computed tomography and chemical shift magnetic resonance imaging
Non-Functional Benign Masses
Among the benign adrenal tumors that don’t produce hormones, the non-functioning adenoma is by far the most common. These are the quintessential incidentalomas: small, bland, and harmless. Another benign type worth knowing about is the myelolipoma, a tumor made of fat and bone marrow tissue. Myelolipomas are almost always found by accident and typically require no treatment.16PubMed Central. Clinical course of adrenal myelolipoma: A long-term longitudinal follow-up study In a long-term study of over 300 myelolipomas, the median size at diagnosis was just 2.3 centimeters, and 86% were incidental findings. Larger myelolipomas, particularly those 6 centimeters or above, are more likely to cause symptoms from their sheer size, develop hemorrhagic changes, and require surgical removal. About half of myelolipomas 6 centimeters or larger eventually underwent adrenalectomy in that study, versus only 5% of smaller ones.16PubMed Central. Clinical course of adrenal myelolipoma: A long-term longitudinal follow-up study Other benign but less common adrenal masses include cysts and ganglioneuromas.
Genetic Connections
Most adrenal tumors are sporadic, meaning they arise without a known inherited cause. But certain genetic syndromes raise the risk substantially. Childhood adrenocortical tumors are particularly linked to Li-Fraumeni syndrome, caused by mutations in the TP53 gene, and to Beckwith-Wiedemann syndrome. In adults, ACC has been reported in patients with multiple endocrine neoplasia type 1 (MEN1), familial adenomatous polyposis, and neurofibromatosis type 1.17PubMed Central. Association of adrenocortical carcinoma with familial cancer susceptibility syndromes
Pheochromocytomas have an even stronger genetic component. Up to 80% of catecholamine-secreting tumors, including pheochromocytomas and paragangliomas, have been found to carry a genetic predisposition. These tumors are associated with hereditary syndromes including MEN2, von Hippel-Lindau disease, and neurofibromatosis type 1.18Ewha Medical Journal. Overview of endocrine tumor syndromes manifesting as adrenal tumors Because the genetic contribution is so large for pheochromocytomas, current practice increasingly favors genetic testing for anyone diagnosed with one, even if there’s no obvious family history.
Diagnosis Beyond Imaging
A CT scan or MRI can reveal an adrenal mass and give clues about its nature, but a complete diagnosis requires hormonal testing. The standard workup typically includes a dexamethasone suppression test to check for cortisol overproduction, measurements of plasma aldosterone and renin to screen for aldosteronism, and plasma or urinary catecholamine metabolites to rule out pheochromocytoma. These tests can be done in stages, and some guidelines recommend screening for all three hormone pathways in any patient with a newly discovered adrenal mass.
An emerging tool is urine steroid profiling, which uses mass spectrometry to measure a panel of steroid hormones and their metabolites in a single urine sample. Adrenocortical carcinomas show a distinctive pattern of immature, early-stage steroid production that differs from benign adenomas. In research settings, steroid profiling has shown the ability to distinguish benign from malignant adrenal tumors with sensitivity and specificity around 90%.19The Journal of Clinical Endocrinology & Metabolism. Urine Steroid Metabolomics as a Biomarker Tool for Detecting Malignancy in Adrenal Tumors This approach offers a non-invasive complement to imaging that could help spare patients from unnecessary surgery.20PubMed. Urine steroid profile as a new promising tool for the evaluation of adrenal tumors. Literature review
Treatment and What Happens After Surgery
For functional tumors causing clinical problems and for masses suspicious for malignancy, surgery is the primary treatment. Since the early 1990s, laparoscopic adrenalectomy has become the standard approach for most adrenal conditions, offering shorter hospital stays and quicker recovery compared to open surgery.21PubMed Central. Laparoscopic adrenalectomy: Surgical techniques For small, clearly benign, non-functional tumors, the usual recommendation is periodic imaging and hormonal follow-up rather than surgery.
Adrenocortical carcinoma demands more aggressive management. Surgery remains the cornerstone, but the drug mitotane, which has a direct toxic effect on adrenal cortex cells, is the main medical treatment for ACC. In an adjuvant setting (given after surgery to prevent recurrence), mitotane significantly extended the time before cancer returned, with a median recurrence-free survival of 42 months in the mitotane group compared to 10 and 25 months in two untreated comparison groups.22PubMed. Adjuvant mitotane treatment for adrenocortical carcinoma Multidisciplinary care also matters: patients with advanced ACC treated by a multidisciplinary team showed substantially better survival than those managed without one.23PubMed Central. The Overall Survival and Progression-Free Survival in Patients with Advanced Adrenocortical Cancer Is Increased after the Multidisciplinary Team Evaluation
One aspect of adrenal surgery that catches patients off guard is post-operative adrenal insufficiency. When one adrenal gland has been overproducing cortisol, the other gland often shrinks and goes dormant because the brain’s hormonal signaling has suppressed it. After the overactive gland is removed, the remaining gland may take weeks or months to wake back up. During that window, patients need glucocorticoid replacement therapy, typically hydrocortisone or prednisone, and the tapering process requires close monitoring.24PubMed Central. Comparison of hydrocortisone and prednisone in the glucocorticoid replacement therapy post-adrenalectomy of Cushing’s Syndrome In some cases, recovery of the remaining gland takes much longer than expected, and factors like the size of the removed tumor and whether the opposite gland was already atrophied on imaging can help predict how long steroid replacement will be needed.25Annals of Medicine and Surgery. Factors predicting prolonged glucocorticoid therapy in patients with adrenal insufficiency after laparoscopic adrenalectomy
Adrenal Tumors in Children
Adrenal tumors in children are far less common than in adults but present differently. In a pediatric retrospective review, tumors arising from the adrenal medulla (neuroblastoma and pheochromocytoma) tended to show up with fever, pain, and a swollen belly, while tumors arising from the cortex most often presented with features of Cushing’s syndrome.26PubMed. Clinical characteristics of adrenal tumors in children: a retrospective review of a 15-year single-center experience Neuroblastoma, a cancer of immature nerve cells, is the most common adrenal malignancy in young children and is unrelated to the adrenocortical carcinomas seen in adults. Childhood ACC, while rare, is notably linked to inherited TP53 mutations, particularly in certain populations where carrier rates of specific TP53 variants are elevated.27PubMed Central. Adrenocortical tumors and hyperplasias in childhood–etiology, genetics, clinical presentation and therapy For this reason, genetic counseling is a standard part of the workup when a child is diagnosed with an adrenocortical tumor.
When a “Non-Functional” Tumor Is Not Truly Harmless
The category of “non-functional” adrenal tumor deserves some skepticism. As testing becomes more sensitive, more tumors previously labeled non-functional turn out to be secreting small amounts of cortisol. The MACS phenomenon, where a tumor produces just enough cortisol to nudge cardiovascular risk factors upward without causing visible Cushing’s features, is a good example of why the old binary of “functioning” versus “non-functioning” oversimplifies reality. Patients with MACS consistently show higher rates of metabolic problems compared to patients whose tumors genuinely produce no excess hormone.5PubMed. Cardiometabolic risk and therapeutic outcomes in mild autonomous cortisol secretion Whether surgical removal of the tumor improves those metabolic outcomes is an area of active research, and the decision to operate on a MACS-producing adenoma often involves weighing the metabolic risks against the surgical risks and the age and overall health of the patient.
This gray zone means that follow-up matters even for tumors initially judged to be quiet. Guidelines generally recommend periodic hormonal re-testing and repeat imaging for at least a few years after an adrenal incidentaloma is discovered, because a small number of initially non-functional tumors begin secreting hormones over time, and a small number of initially benign-looking masses prove to be slow-growing malignancies.