An adrenal incidentaloma is an adrenal tumor that is discovered on an imaging test that is being done for a problem unrelated to adrenal disease. Adrenal tumors found as part of the work-up or follow-up of cancer are very likely to be adrenal metastases and do not count as adrenal incidentalomas. As imaging techniques have improved and become more commonly used, doctors are finding more and more adrenal incidentalomas. The chance of having an adrenal incidentaloma increases with increasing age. At the age of 50, there is a 3% risk of having an adrenal incidentaloma and this goes up to 7% by the age of 70. While most adrenal incidentalomas do not cause health problems, they must be evaluated because a small percentage can lead to significant disease.
Adrenal incidentalomas fall into one of three categories:
- Functioning tumors these tumors make too much of any of the hormones that the adrenal glands normally make and include aldosterone-producing adenomas (See Primary Hyperaldosteronism), cortisol producing tumors (See Cushing's Syndrome), adrenaline producing tumors (See Pheochromocytoma), or sex-hormone producing tumors (See Sex-hormone Producing Tumors).
- Malignant tumors these tumors include adrenocortical cancer and metastatic disease.
- Benign, non-functional tumors these tumors include adenomas, myelolipomas, ganglioneuromas, adrenal cysts, and hematomas.
In general, tumors that are functional, malignant, and/or large should be removed.
Signs and Symptoms
By definition, adrenal incidentalomas are asymptomatic. However, once an adrenal incidentaloma is discovered, closer questioning and examination may reveal symptoms.
Work-up of Adrenal Incidentaloma
In determining the treatment of adrenal incidentaloma, two questions must be asked: 1) is it functional and 2) is it cancer (i.e. malignant).
Is it functional?
The three functional tumors to rule out are aldosterone-producing adenoma, cortisol-producing tumors, and pheochromocytoma. In order to do this, patients should have hormone testing that includes plasma aldosterone and renin levels (See Primary Hyperaldosteronism > Diagnosis), a low dose dexamethasone suppression test (See Cushing’s Syndrome > Diagnosis), and plasma or urine metanephrines levels (See Pheochromocytoma > Diagnosis).
Is it cancer?
The two types of cancer to rule out are metastatic disease to the adrenal gland and adrenocortical cancer. Patients should have age-appropriate health screening including colonoscopy, chest X-ray, skin examination, and mammogram (if appropriate) as directed by their physician to see if this is metastatic disease to the adrenal gland. If there is a high suspicion of metastatic disease, then a special nuclear medicine test called a PET scan may be ordered to look for cancer elsewhere in the body. (See Adrenal Metastases)
|Size||Risk of Adrencortical Cancer|
|Smaller than 4 cm||3%|
|4 to 6 cm||7%|
|Bigger than 6 cm||25%|
Size and appearance on imaging can help assess the risk for adrenocortical cancer in an adrenal incidentaloma. enign tumors generally have smooth borders, a Hounsfield unit (i.e. a measure of how dense different tissues are on CAT scan) less than 10, and/or are neutral on T2-weighted MRI. If a tumor is bright on T2-weighted MRI, has a Hounsfield unit greater than 10 on CAT scan, irregular borders, or evidence of invasion into surrounding organs, it is likely to be malignant. Size is the best indication of cancer in an adrenal incidentaloma. The larger the tumor the higher the risk of adrenocortical cancer.
In very rare cases, a biopsy of the tumor may be done to see if it is metastatic disease. However, a biopsy must NOT be done until a pheochromocytoma is ruled out. Performing a biopsy on a pheochromocytoma may lead to a life threatening “pheo crisis.” (See Pheochromocytoma > Signs and Symptoms)
Functional adrenal incidentalomas should be removed. For patients with non-functional tumors, the risk of adrenocortical cancer based on size and imaging characteristics will determine if they should be removed. Tumors that appear suspicious for cancer on imaging should be removed. The guidelines for removing adrenal incidentaloma based on size are as follows:
|Size||Risk of Adrencortical Cancer||Recommendation|
|Smaller than 4 cm||3%||Observation|
|4 to 6 cm||7%||Adrenalectomy if the patient is healthy enough|
|Bigger than 6 cm||25%||Adrenalectomy|
In general, tumors over 6 cm in size should be removed and tumors over 4 cm in size should be removed if the patient is healthy enough to tolerate the operation. Since CAT scan and MRI tend to underestimate the size of adrenal tumors, some physicians recommend observing tumors less than 3 cm, removing tumors between 3 and 5 cm if the patient is healthy enough, and removing all tumors greater than 5 cm. Most adrenal incidentalomas can be removed using minimally invasive techniques such as laparoscopy. (See Adrenal Surgery)
For small, non-functional tumors that are being observed, the patient should have hormonal testing every year for 5 years and repeat imaging every 6 months to a year for a few years. Studies have shown that 25% of adrenal incidentaloma will grow and up to 20% will become functional over time. Of those that become functional, most develop Cushing's syndrome.