[Diagnostic and therapeutic strategy for an incidental finding of an adrenal mass]

Abstract

The incidental finding of an unsuspected adrenal mass ranges from 0.5% to 5% in abdominal CT series. The optimal diagnostic approach to such masses is to diagnose malignant or secretory tumors requiring excision and to otherwise avoid unnecessary surgery. Physical examination generally contributes little. A standard biochemical evaluation should include the measurement of 24 hour urinary catecholamines and metanephrine, urinary free cortisol and plasma cortisol levels at 8 a.m. and 8 p.m. combined with an overnight low-dose dexamethasone suppression test, serum potassium assay, and determination of upright plasma aldosterone to plasma renin activity. These tests will serve to screen for pheochromocytoma, subclinical Cushing's syndrome, and primary hyperaldosteronism respectively. Imaging characteristics suggestive of malignancy include: size greater than 4 cm., heterogeneous lesion and/or density greater than 20 Hounsfield Units on CT scan, slow enhancement with delayed washout after intravenous contrast injection on CT scan, and slightly decreased signal intensity in out of phase (fat suppressed) MR acquisition. Fine-needle aspiration biopsy should be performed only if metastatic disease is suspected. Adrenal scintigraphy with iodocholesterol may be useful where adenoma with subclinical Cushing's syndrome or solid tumor is suspected. In summary, the following strategy is recommended for the management of adrenal incidentalomas : mass lesions larger than 4 cm. and hormone-secreting tumors should be removed. All non-secreting adrenal incidentalomas smaller than 4 cm. in diameter should be followed by serial imaging at regular intervals (6, 12, and 36 months) and by endocrine reevaluation at one year.