How to Handle "Incidentalomas"

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The author discusses what to do when testing for another cause turns up an incidental finding of adrenal adenoma.


Maggie, 42, presents to the emergency department with chronic intermittent abdominal pain and bloating with constipation and occasional diarrhea. She denies fever, chills, nausea, vomiting, melana, bright red blood per rectum, or changes in stool caliper, and she says she otherwise feels well.

Relevant lab and study results include: a comprehensive metabolic panel, complete blood count with differential, beta hCG (human chorionic gonadotropin), urinalysis, and amylase and lipase, all within normal limits; pregnancy test, negative; abdominal x-ray, within normal limits except increased stool in distal colon; and abdominal CT, 2.3-cm right adrenal mass and a Hounsfield measurement of 4 units.

Maggie has a right adrenal incidentaloma (incidentally discovered adenoma that was not in the differential diagnosis). Such findings have become all too often the case, due to the immediate access to and overutilization of high-resolution CT, MRI, and ultrasound. We are now seeing a significantly increased number of incidental adrenal lesions/masses discovered on images not intended to look for adrenal-related diseases (eg, Cushing syndrome, pheochromocytomas, and aldosterone-producing adenomas).

Q: How common are adrenal adenomas, and what must I consider?

Incidental adrenal adenomas are found on 4.4% of abdominal CTs, and in one autopsy series were discovered in 8.7%. Prevalence increases with age, with occurrence of < 1% in patients younger than 30 and about 7% for patients 70 or older.

Evaluation is based on two concerns: First, is the adrenal mass benign or malignant? Second, is the mass secretory or nonsecretory (non-hormone secreting) in nature?

The fortunate news about adrenal incidentalomas is that 80% are benign and nonsecretory, which provides immediate reassuring news to the patient. Examples of benign adrenal masses are: adenoma, lipoma, cyst, ganglioneuroma, hematoma, and infection (eg, tuberculosis, fungal).

The other encouraging statistic is that only 1:4,000 adrenal incidentalomas are malignant. Examples of malignant adrenal masses are: adrenocortical carcinoma, metastatic neoplasm, lymphoma, and malignant pheochromocytoma.

Q: Does adrenal adenoma size matter?

Yes, the larger the size of the adenoma, the higher the association with malignancy. The guide below (based on CT findings) shows not only malignancy potential as it relates to size, but also the importance of Hounsfield units and when surgical intervention is recommended.

Imaging (CT scan)

< 4 cm: homogeneous mass with smooth borders and < 10 Hounsfield units; suggests benign mass (likelihood of malignancy, about 2%)

4 to 6 cm: follow closely, consider surgery (likelihood of malignancy, about 6%)

> 6 cm: surgery indicated (likelihood of malignancy, about 25%)

Some providers and patients inquire whether it is helpful or necessary to biopsy. It is generally not advisable to biopsy, especially if the findings are favorable for benign nonsecretory masses, since there is a high false-negative rate. An indication for biopsy is if the patient has a history of extra-adrenal malignancy; this will distinguish recurrence or metastatic disease from a benign mass. A final proviso: If biopsy is performed, make sure the adrenal mass is not a pheochromocytoma, as biopsy of a hormone-secreting neoplasm can lead to a hypertensive emergency.

Q: How do I determine whether the mass is hormone-secreting?

Although 80% are nonsecretory, you must still maintain a high index of suspicion so as not to miss a potentially problematic and fully treatable adenoma. A thorough history is essential in screening for hormonal excess arising from adrenal adenomas, since the signs and symptoms can be insidious. The three hormones secreted by adrenal adenomas are cortisol, aldosterone, and catecholamines (seen in Cushing syndrome, aldosterone-producing adenoma [APA], and pheochromocytoma, respectively).

It is important to note that Cushing syndrome has an insidious onset and can be easily missed. Hyperaldosteronism presents with hypertension (requiring several medications) and commonly hypokalemia. And pheochromocytoma can be “written off as” anxiety disorder, panic attack, or even hypoglycemia symptoms (especially if patients are treated for diabetes with agents that cause hypoglycemia). To help in your differential diagnosis of secretory adenomas, know that APA accounts for only 1%, and therefore the majority will secrete cortisol and (far less likely) catecholamines.

Q: What is the appropriate laboratory work-up?

The best simple screening test for hypercortisolemia is a 1-mg overnight dexamethasone suppression test. If this value is increased to ≥ 3 µg/dL, it should be followed up with a more sensitive test (a 24-hour urine for creatinine and free cortisol) to further assess for hypercortisolemia.

Patients thought to have a potential pheochromocytoma should undergo measurement of plasma fractionated metanephrines and normetanephrines or 24-hour urine for total metanephrines and fractionated catecholamines.

Finally, for patients with hypokalemia and hypertension or refractory hypertension requiring multiple (> 3) antihypertensive medications, plasma renin activity (PRA) and plasma aldosterone concentration (PAC) should be obtained. A low PRA and a PAC > 15 ng/dL, along with a PAC/PRA ratio of > 20, is highly suggestive of an APA.

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