1. Introduction
An adrenal mass is an abnormal growth of tissue located on one or both of the adrenal glands, which are small, triangular endocrine glands situated directly on top of the kidneys. The vast majority of these masses are discovered purely by chance when a patient undergoes abdominal imaging, such as a CT scan or MRI, for an unrelated medical reason. In the medical community, a mass found in this manner is referred to as an adrenal incidentaloma.
Finding a mass on an internal organ naturally causes significant anxiety for the patient. However, it is clinically reassuring to note that the overwhelming majority of adrenal masses are benign, non-cancerous growths that do not cause any symptoms or harm. Nonetheless, every adrenal mass requires a systematic and careful medical evaluation.
The clinical assessment focuses on answering two critical questions: Is the mass malignant (cancerous), and is it producing an excess of hormones? Because the adrenal glands are major hormone-producing centers, even a benign tumor can cause profound health issues if it secretes excessive amounts of adrenaline, cortisol, or aldosterone. This article details the function of the adrenal glands, the diagnostic workup, and the management of adrenal masses.
2. Anatomy and Function of the Adrenal Glands
To understand the implications of an adrenal mass, one must understand the organ’s anatomy and physiology. The adrenal gland is divided into two distinct zones, each responsible for producing different critical hormones. The outer layer is the adrenal cortex, and the inner core is the adrenal medulla.
The adrenal cortex produces steroid hormones necessary for life. These include glucocorticoids, primarily cortisol, which regulates metabolism and the body’s response to stress. It also produces mineralocorticoids, like aldosterone, which control blood pressure by managing the balance of sodium and potassium. Additionally, the cortex secretes small amounts of sex hormones (androgens).
The inner adrenal medulla is part of the sympathetic nervous system. It produces catecholamines, primarily epinephrine (adrenaline) and norepinephrine. These hormones are responsible for the body’s rapid “fight or flight” response, sharply increasing heart rate and blood pressure in response to acute stress. A mass in either region can disrupt these delicate hormonal balances.
3. What is an Adrenal Incidentaloma?
The widespread use of high-resolution abdominal imaging has led to a significant increase in the discovery of adrenal incidentalomas. Studies suggest that up to 5% of all abdominal CT scans performed reveal an unexpected adrenal mass. The incidence increases with patient age, making them a common clinical finding in older adults.
The term “incidentaloma” strictly refers to tumors found unexpectedly, not those discovered during a workup for symptoms of adrenal disease or in a patient with a known active cancer undergoing staging. The primary medical challenge with an incidentaloma is avoiding unnecessary, invasive surgeries while ensuring that harmful hormone-secreting tumors or rare cancers are not missed.
Following discovery, current endocrine guidelines dictate that all patients with an incidentaloma undergo a standardized series of biochemical blood and urine tests, along with a careful analysis of the imaging characteristics, to risk-stratify the lesion and determine the appropriate course of action.
4. Non-Functioning Benign Adenomas
The most frequent diagnosis for an adrenal mass is a non-functioning benign cortical adenoma. These tumors originate in the adrenal cortex but lack the biochemical machinery to overproduce hormones. They are biologically inert, meaning they sit on the gland without causing any systemic effects.
A non-functioning adenoma is typically small, usually measuring less than 4 centimeters in diameter. On imaging, they have characteristic features, such as a high fat content, which makes them easily identifiable to a radiologist. Because they are benign and inactive, they do not cause symptoms like weight gain, high blood pressure, or pain.
For patients diagnosed with a small, non-functioning adenoma, surgical removal is rarely recommended. The standard of care involves active observation. The patient will typically undergo repeat imaging and hormone testing over the next 12 to 24 months to ensure the mass does not grow significantly or begin secreting hormones.
5. Hormone-Secreting Tumors: An Overview
When an adrenal mass is biologically active, it is termed a “functioning” tumor. These tumors autonomously produce and secrete hormones into the bloodstream, bypassing the body’s normal regulatory feedback mechanisms. The clinical symptoms a patient experiences depend entirely on which specific hormone is being overproduced.
Functioning tumors can be either benign adenomas or, much less commonly, malignant carcinomas. The excess hormones disrupt normal metabolic and cardiovascular homeostasis. Because the symptoms can be vague and overlap with common conditions like essential hypertension or general obesity, the underlying adrenal cause is sometimes overlooked for years.
The diagnostic workup requires precise endocrine laboratory testing to measure the levels of hormones and their breakdown products in the blood and urine. Identifying the specific hormone excess is the first step toward appropriate medical or surgical management.
6. Pheochromocytoma and Adrenaline
A pheochromocytoma is a rare, functioning tumor that originates in the adrenal medulla and secretes excessive amounts of catecholamines (adrenaline and norepinephrine). While mostly benign, they are highly dangerous because the surges of adrenaline they release can cause catastrophic cardiovascular events.
The classic clinical presentation of a pheochromocytoma includes sudden, severe episodes of high blood pressure accompanied by a pounding headache, profound sweating, and a rapid, racing heartbeat. These “spells” can last from a few minutes to an hour and often occur unpredictably.
Diagnosis is made by measuring fractionated metanephrines, the breakdown products of adrenaline, in the blood or in a 24-hour urine collection. If confirmed, a pheochromocytoma requires surgical removal. Crucially, surgery must be preceded by careful medical preparation using specific blood pressure medications (alpha-blockers) to prevent a life-threatening hypertensive crisis during the operation.
7. Cushing’s Syndrome and Cortisol Excess
An adrenal mass that overproduces cortisol causes a condition known as Cushing’s syndrome. Cortisol is the body’s primary stress hormone, and chronic exposure to high levels profoundly alters metabolism, immune function, and body composition.
Patients with adrenal Cushing’s syndrome often present with rapid, unexplained weight gain, particularly centralized around the abdomen and face (resulting in a round “moon face”). Other symptoms include thinning of the skin, easy bruising, purple stretch marks on the abdomen, severe muscle weakness, and the onset of diabetes and hypertension.
Endocrinologists diagnose cortisol excess using several tests, the most common being the 1mg overnight dexamethasone suppression test. The patient takes a synthetic steroid pill at night, and blood cortisol is measured the next morning. A healthy system will suppress cortisol production, while an autonomous adrenal tumor will continue to produce high levels.
8. Conn’s Syndrome and Aldosterone
When a benign adrenal adenoma secretes excessive amounts of aldosterone, it causes primary aldosteronism, often referred to as Conn’s syndrome. Aldosterone acts on the kidneys to retain sodium and excrete potassium, leading to increased blood volume and elevated blood pressure.
Conn’s syndrome is a significant, yet frequently underdiagnosed, cause of secondary hypertension. Patients typically present with high blood pressure that is resistant to multiple standard medications. They may also experience muscle cramps, weakness, and excessive urination due to low potassium levels in the blood (hypokalemia).
The initial screening test is a blood draw to calculate the aldosterone-to-renin ratio. A high ratio indicates that the adrenal gland is producing aldosterone inappropriately, despite low levels of renin (the kidney enzyme that normally stimulates its production). Confirmation tests and specialized imaging are then used to localize the problematic mass.
9. Adrenocortical Carcinoma
Adrenocortical carcinoma is a primary cancer of the adrenal gland. Fortunately, it is extremely rare, affecting only 1 to 2 people per million annually. However, it is a highly aggressive malignancy. These tumors are often quite large at the time of discovery, frequently exceeding 4 to 6 centimeters in diameter.
Adrenocortical carcinomas can be either functioning or non-functioning. Functioning carcinomas often secrete multiple types of hormones simultaneously, leading to a rapid onset of complex symptoms, such as combining features of Cushing’s syndrome with excessive androgen production, causing masculine traits in females (hirsutism).
On imaging, these masses appear heterogeneous, irregular, and often show signs of invading nearby structures like the kidney or the large abdominal veins. Treatment requires expert oncological and surgical care, usually involving complete surgical resection of the adrenal gland and adjacent tissues, followed by specific chemotherapy.
10. Metastatic Adrenal Tumors
Because the adrenal glands have a very rich blood supply, they are a common site for other cancers to spread (metastasize). A mass found in the adrenal gland is frequently the result of metastatic disease, particularly in a patient with a known history of cancer.
The most common primary cancers that metastasize to the adrenal glands include lung cancer, breast cancer, melanoma, and renal cell carcinoma. Unlike functioning adenomas, metastatic tumors do not produce adrenal hormones, though they can sometimes destroy enough adrenal tissue to cause adrenal insufficiency.
If a patient with a history of cancer is found to have a new adrenal mass, the suspicion for metastasis is very high. A fine-needle biopsy may be performed in this specific scenario to confirm the cellular origin of the tumor and guide systemic oncological treatment.
11. Initial Diagnostic Imaging
The characterization of an adrenal mass relies heavily on advanced radiological imaging. An unenhanced (without contrast) CT scan of the abdomen is the standard initial imaging modality. Radiologists evaluate the mass based on its size, its shape, and its density, which is measured in Hounsfield Units (HU).
Benign adenomas are rich in lipids (intracellular fat). Fat has a low density on a CT scan. Therefore, a smooth, homogenous adrenal mass with a density of less than 10 HU is almost definitively a benign, lipid-rich adenoma, and generally requires no further imaging workup to prove it is non-cancerous.
If the mass has a density greater than 10 HU, it is considered lipid-poor. This requires further characterization using a specialized CT protocol called “adrenal washout.” This test measures how quickly the intravenous contrast dye washes out of the mass over 15 minutes. Benign adenomas wash out contrast quickly, while malignant or metastatic lesions tend to retain the dye.
12. Data Summary: Evaluating an Adrenal Mass
The table below summarizes the key features used to differentiate the common types of adrenal masses during a clinical workup.
| Type of Adrenal Mass | Hormone Status | Typical CT Scan Characteristics |
|---|---|---|
| Benign Cortical Adenoma | Usually non-functioning. | Small (<4 cm), homogenous, low density (<10 HU), rapid contrast washout. |
| Pheochromocytoma | High catecholamines. | Variable size, highly vascular, retains contrast dye. |
| Adrenocortical Carcinoma | Often functioning (mixed hormones). | Large (>4-6 cm), irregular margins, high density, necrosis or calcification present. |
| Metastatic Lesion | Non-functioning. | Irregular, delayed contrast washout, often bilateral. |
This structured approach ensures that patients with harmless adenomas avoid unnecessary surgery, while dangerous tumors are identified quickly.
13. Endocrine Laboratory Testing
Following the initial radiological assessment, every patient with an adrenal incidentaloma must undergo biochemical testing. Even if the patient feels perfectly well, a functioning tumor must be ruled out. The testing protocols are strictly defined by endocrinology guidelines.
The standard screening panel includes the 1mg overnight dexamethasone suppression test to rule out silent cortisol excess, and plasma free metanephrines to rule out a pheochromocytoma. If the patient has hypertension, an aldosterone and renin level will also be drawn to check for primary aldosteronism.
Testing for sex hormones, such as DHEA-S or testosterone, is usually reserved for masses that exhibit suspicious imaging characteristics or in patients showing clinical signs of hormone imbalance. Accurate interpretation of these laboratory tests is complex and is best managed by a specialist in endocrinology.
14. Observation and Active Surveillance
If the radiological and biochemical workup concludes that the adrenal mass is small (less than 4 cm), benign in appearance, and non-functioning, the standard recommendation is active surveillance. Surgery is not indicated, as the risks of an operation outweigh the risks posed by a harmless adenoma.
Surveillance typically involves repeating the unenhanced CT scan in 6 to 12 months to confirm the mass is not growing rapidly. A growth rate of less than 1 centimeter per year is generally reassuring. The endocrine laboratory tests are also often repeated annually for up to four years to ensure the mass does not slowly become biologically active.
Patients should maintain regular check-ups with their primary care physician. Just as understanding the pathology of a peritumoral lymphocytic response provides clarity in cancer care, understanding the inert nature of a benign adenoma helps patients avoid unnecessary anxiety during the surveillance period.
15. Surgical Management (Adrenalectomy)
Surgical removal of the adrenal gland, a procedure known as an adrenalectomy, is the definitive treatment for several specific clinical scenarios. Surgery is strictly recommended for any adrenal mass that is proven to be autonomously secreting excessive hormones, regardless of its size.
Surgery is also advised for any mass that is larger than 4 to 6 centimeters, or any mass that shows suspicious radiological features suggesting adrenocortical carcinoma, regardless of hormone status. In cases of suspected malignancy, open abdominal surgery is generally preferred to ensure the mass is removed completely without rupturing the tumor capsule.
For benign, functioning tumors (like small pheochromocytomas or aldosterone-producing adenomas), a minimally invasive laparoscopic or robotic adrenalectomy is the standard approach. This technique offers a shorter recovery time, less post-operative pain, and smaller scars. Following surgery, the remaining healthy adrenal gland usually assumes full hormone production for the body.
16. Frequently Asked Questions (FAQ)
1. Is an adrenal mass a type of cancer?
The vast majority of adrenal masses are benign (non-cancerous) adenomas. Primary adrenal cancer is extremely rare. Your doctor uses imaging and blood tests to differentiate between benign and malignant masses.
2. Will I need surgery to remove the mass?
Surgery is only required if the mass is cancerous, suspicious for cancer (usually due to large size or irregular imaging), or if blood tests confirm it is producing excessive amounts of hormones that harm your body.
3. What happens if I have an adrenal gland removed?
Humans have two adrenal glands. If one is surgically removed, the remaining healthy gland is usually capable of producing all the necessary hormones your body needs to function normally.
4. Can an adrenal mass cause high blood pressure?
Yes. If the mass is a functioning tumor that secretes excessive adrenaline (pheochromocytoma) or aldosterone (Conn’s syndrome), it can cause severe, difficult-to-treat high blood pressure.
5. How long does the testing process take?
The initial workup involves a CT scan and specific blood and urine tests. The entire diagnostic process can usually be completed within a few weeks, allowing your doctor to formulate a definitive management plan.
17. Bibliography
Disclaimer: The content is for informational purposes only and does not replace medical advice. Always consult your doctor for personalized treatment.
