The adrenal glands are small, triangular-shaped organs situated in the upper abdomen, resting directly on top of each kidney. They are a crucial part of the endocrine system, producing hormones like cortisol, aldosterone, and adrenaline that regulate metabolism, blood pressure, and the body’s response to stress.
An adrenal lesion, often called an adrenal mass or nodule, is any abnormal growth found on one or both glands, such as a tumor, cyst, or localized tissue enlargement. The discovery of such a mass warrants a comprehensive evaluation to determine its nature and whether it is affecting the body’s hormone production.
Understanding the Types of Adrenal Lesions
Adrenal lesions are classified based on two main characteristics: malignancy and functionality. The most common type is the benign adenoma, which is non-cancerous and represents 80 to 90% of all discovered adrenal masses. These benign lesions are composed of tissue similar to the adrenal cortex and do not pose a cancer risk.
Malignant lesions are far less common. They include primary adrenal cancer, known as adrenocortical carcinoma, and metastatic lesions. Metastatic lesions are cancers that have spread to the adrenal gland from another primary site, most commonly the lung, breast, or kidney. The presence of known cancer elsewhere significantly changes the evaluation of an adrenal mass.
Functionality refers to whether the mass actively secretes hormones in excessive amounts. A non-functional lesion is hormonally silent and does not disrupt the body’s hormone balance. Functional lesions, however, overproduce hormones and can lead to specific medical conditions.
For example, excessive cortisol production causes Cushing’s Syndrome. Overproduction of aldosterone results in Conn’s Syndrome, often leading to high blood pressure and low potassium. A lesion that secretes excessive adrenaline and noradrenaline is called a pheochromocytoma, which can cause severe, episodic high blood pressure, headaches, and palpitations.
How Adrenal Lesions Are Typically Discovered
The most frequent way an adrenal lesion is found is through an “adrenal incidentaloma.” This term applies to a mass discovered incidentally on an imaging scan, such as a CT or MRI, performed for an unrelated medical reason, like evaluating kidney stones or back pain. Up to 4% of people undergoing abdominal imaging are found to have an adrenal incidentaloma.
These accidentally discovered masses are often non-functional and do not cause noticeable symptoms. The growing use of advanced cross-sectional imaging has led to a significant increase in the discovery of these silent lesions. For many individuals, the mass is a benign finding that requires no intervention beyond monitoring.
In contrast, some lesions are discovered because they cause symptoms related to their size or, more commonly, their excessive hormone production. For instance, a patient evaluated for unexplained, difficult-to-control high blood pressure may be checked for an aldosterone-producing lesion. Less frequently, a very large mass may cause localized pain or a feeling of fullness, prompting imaging that reveals the growth.
The Diagnostic Evaluation Process
Once an adrenal lesion is discovered, a standardized diagnostic workup is initiated to answer two main clinical questions: is the mass functional and is it malignant? This evaluation involves specialized hormonal testing and a close analysis of the mass’s appearance on imaging. Hormonal evaluation is essential for all patients, even those without symptoms, to screen for subclinical hormone excess.
To check for cortisol overproduction, a 1-milligram overnight Dexamethasone Suppression Test is performed, measuring blood cortisol after a dose of synthetic steroid is taken the night before. Testing for a pheochromocytoma involves measuring plasma free metanephrines or 24-hour urinary fractionated metanephrines, which are breakdown products of adrenaline and noradrenaline. The Aldosterone-to-Renin Ratio is measured in patients with hypertension or low potassium to screen for Conn’s syndrome.
Initial CT imaging characteristics provide valuable clues about the risk of malignancy. A key measurement is the density of the mass, expressed in Hounsfield units (HU) on a non-contrast CT scan. A density of 10 HU or less is highly suggestive of a benign, lipid-rich adenoma due to the fat content within the mass. Lesions greater than 10 HU are considered indeterminate and require further assessment.
For indeterminate masses, a contrast-enhanced CT with a washout protocol is often used to differentiate benign from malignant tissue. Benign adenomas rapidly release or “wash out” the contrast dye. An absolute washout of 60% or more, or a relative washout of 40% or more, confirms the mass as a benign adenoma with a high degree of certainty.
Treatment and Long-Term Management
Management of an adrenal lesion falls into two main pathways: active surveillance or surgical removal. Active surveillance, often called watchful waiting, is the standard approach for lesions that are non-functional and demonstrate benign characteristics on imaging, such as a density of 10 HU or less. This strategy involves periodic follow-up with repeat imaging, typically a CT scan, and repeat hormonal blood tests.
If the mass is small, non-functional, and stable in size, follow-up may be discontinued after several years. A mass exhibiting minimal growth (less than 3 millimeters per year) is also considered stable and can continue to be monitored. The goal of surveillance is to detect any late-onset hormone production or significant growth.
Surgical removal of the adrenal gland, known as adrenalectomy, is recommended for functional lesions, such as those causing Cushing’s syndrome or pheochromocytoma, regardless of size. Surgery is also necessary for non-functional masses that are large or have suspicious imaging features. The general size threshold for considering removal is 4 centimeters, as the risk of malignancy increases significantly above this size.
For masses exceeding 6 centimeters, the risk of adrenocortical carcinoma is high enough that immediate surgery is usually recommended. Adrenalectomy is performed using minimally invasive techniques, such as laparoscopic or robotic surgery, whenever possible, allowing for smaller incisions and a faster recovery.