An adrenal incidentaloma is a mass discovered on the adrenal gland entirely by chance during a medical imaging test performed for an unrelated reason. This finding typically refers to a mass greater than one centimeter in diameter that was not suspected based on the patient’s symptoms. The overall prevalence is estimated to be between two and three percent in the general population, rising significantly with age. The diagnosis initiates a systematic medical investigation to determine the mass’s nature and whether it poses a health risk.
The Role of the Adrenal Glands
The adrenal glands are two small, triangular-shaped endocrine organs situated atop each kidney. These glands are composed of two distinct parts: the outer cortex and the inner medulla, each producing different hormones. The outer adrenal cortex synthesizes steroid hormones, primarily cortisol and aldosterone. Cortisol helps regulate metabolism, manages the body’s stress response, and influences the immune system. Aldosterone regulates blood pressure by controlling the balance of salt and water. The inner adrenal medulla produces catecholamines, including epinephrine and norepinephrine, which are involved in the body’s rapid “fight-or-flight” response.
The Nature of Incidental Discovery
These masses are most frequently detected through cross-sectional imaging techniques such as Computed Tomography (CT) scans or Magnetic Resonance Imaging (MRI) of the abdomen. A patient may have undergone a scan for symptoms like persistent abdominal pain, kidney stones, or for cancer staging of an extra-adrenal malignancy. The rate at which these incidental masses are found is steadily rising, a trend linked to the widespread use and increasing resolution of modern medical imaging technology. In individuals over the age of 70, the prevalence of finding an adrenal mass on a scan can be as high as ten percent.
Assessing Function and Cancer Risk
Upon discovery, the two primary concerns for medical professionals are whether the mass is producing excess hormones and whether it is malignant. The first step in the assessment involves thorough biochemical testing to evaluate for hormonal overproduction, even if the patient exhibits no obvious symptoms. This screening typically includes measuring levels of cortisol, aldosterone, and catecholamines or their metabolites, such as metanephrines.
If the mass is “functioning,” it means it is autonomously producing hormones above normal levels, which can lead to specific conditions. Excess cortisol can cause Cushing’s syndrome or the more subtle subclinical hypercortisolism, which is the most frequent hormonal abnormality found in incidentalomas. Overproduction of aldosterone may result in primary aldosteronism, or Conn’s syndrome, a common cause of secondary hypertension. Elevated levels of catecholamines are characteristic of a pheochromocytoma, a rare tumor that can cause dangerous spikes in blood pressure.
The second major concern is the risk of malignancy, with most adrenal incidentalomas proving to be benign, non-cancerous tumors called adenomas. The mass’s size and its characteristics on imaging are the main indicators used to assess cancer risk. Masses that measure over four to six centimeters in diameter are viewed with greater suspicion, as the risk of adrenocortical carcinoma increases significantly above this size threshold. For instance, the risk of malignancy in masses larger than six centimeters can be as high as 37.7 percent.
Imaging characteristics on a non-contrast CT scan are particularly informative. Benign adenomas often contain a high amount of fat, causing them to appear “lipid-rich” with a low density, typically measured as ten Hounsfield units (HU) or less. A mass that is lipid-poor, having a density greater than ten HU, is considered indeterminate or suspicious and requires further investigation. These imaging and biochemical assessments guide the decision on whether the mass requires ongoing monitoring or immediate removal.
Monitoring and Treatment Options
The management strategy for an adrenal incidentaloma is determined entirely by the findings from the hormonal and imaging assessments. For the majority of patients, the mass is found to be non-functioning, small, and radiologically benign, which leads to a strategy of active surveillance, or watchful waiting. This involves scheduled follow-up appointments to ensure the mass does not grow and remains hormonally inactive.
Active surveillance protocols typically include repeat imaging, such as a CT or MRI, within six to twelve months of the initial discovery, and then annually for the next one to two years. The patient will also undergo repeat hormonal testing on a yearly basis for up to five years, especially if the mass is greater than three centimeters. This long-term monitoring aims to detect any change in size or the delayed onset of hormonal overproduction, which would necessitate a change in the treatment plan.
Surgical removal, known as adrenalectomy, is recommended when the incidentaloma meets specific high-risk criteria. These indications include a mass size consistently greater than four to six centimeters, imaging features highly suspicious for malignancy, or confirmation of a functioning tumor causing hormonal excess. Most surgical procedures utilize minimally invasive techniques, such as laparoscopic adrenalectomy, to remove the mass and minimize recovery time. Surgery is often the definitive treatment for hormonally active tumors, such as pheochromocytoma or aldosteronoma, that cannot be effectively managed with medication alone.