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Adrenal incidentalomas
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Unexpected findings on imaging studies pose more of a dilemma for clinicians than an abnormal result on a set of lab tests. Infrequently will a surprise abnormal lab result set us to thinking that the patient might have an underlying malignancy. Yet that is often the first concern when an incidentaloma is found on an imaging study.
The most common endocrine incidentaloma is probably a thyroid nodule but that can usually be resolved by fine needle aspiration to rule out (most common) or rule in a thyroid malignancy. Increasingly tiny thyroid lesions too small to biopsy are reported in patients who have head and neck computed tomography in the emergency department or a carotid ultrasound. Check thyroid function, treat if abnormal and get a follow-up ultrasound in six months.
Far more troubling are adrenal incidentalomas which may be discovered in 5% or more of persons having an abdominal CT or magnetic resonance imaging, with the likelihood increasing with age. These lesions are not amenable to biopsy and the onus rests with the clinician to determine if the patient has a functioning tumor and also the likelihood of it being malignant.
Lesions over 6 cm are more likely to be malignant and should be surgically removed – after making sure that the patient does not have a functional tumor that needs to be controlled pre-, peri-, and post-operatively. Lesions under 4 cm are most likely to be benign while those 4-6cm are indeterminate and need careful watching. Careful watching means more than just repeating the imaging study every few months — it is critical that the follow-up be done with the same technology and that the same radiologist reviews the baseline and follow-up studies.
The hormonal evaluation should be done in all patients and include a search for hypercortisolism, pheochromocytoma, and, in hypertensive patients, an aldosteroma. A pheochromocytoma clearly needs intervention when diagnosed but there is still a quandary about what to do about patients with an adrenal incidentaloma and excess cortisol production without clinical manifestations (sub-clinical Cushing’s). Keep an eye on the blood pressure, glucose and bone density and you should pick up the earliest evidence of clinical disease.