Adrenal Mass

1. Epidemiology
   1. Incidental Adrenal Mass found on up to 3-4% of Abdominal CTs or MRIs
   2. Incidental Adrenal Masses found in 20% of autopsies
2. Differential Diagnosis of Incidental Adrenal Mass
   1. Adrenal Adenoma (51%)
      1. Non-functioning adenoma
      2. Functioning adenoma
         1. Cushing's Syndrome
         2. Pheochromocytoma
         3. Hyperaldosteronism
   2. Metastatic cancer (31%)
      1. Bronchogenic Carcinoma
      2. Renal cell carcinoma
      3. Melanoma
   3. Adrenal Carcinoma (1-4%)
   4. Adrenal Cyst (4%)
   5. Pheochromocytoma (4%)
   6. Adrenal Hyperplasia (2%)
   7. Lipoma (2%)
   8. Myelolipoma (2%)
3. Labs
   1. Pheochromocytoma Screening
      1. Consider plasma free metanephrines (in all patients)
      2. 24-hour Urine Metanephrines
      3. 24-hour Urine Vanillylmandelic Acid (VMA)
   2. Cushing's Syndrome Screening
      1. Dexamethasone Suppression Test (in all patients)
      2. 24-hour Urinary free cortisol level
   3. Hyperaldosteronism Screening (hypertensive patients)
      1. Serum Potassium
      2. Plasma aldosterone to renin activity ratio
4. Imaging
   1. CT Abdomen
      1. With IV contrast
      2. With delayed-phase (to perform washout calculations)
   2. MRI Abdomen
      1. With Chemical Shift
      2. Indicated if CT with IV contrast contraindicated
   3. Fluorodeoxyglucose-positron emission testing (FDG-PET)
      1. Indicated for lesions not definitively characterized on CT or MRI
      2. High Test Sensitivity for malignancy
      3. Decreased Test Specificity for malignancy (false positives possible)
5. Evaluation: Reassuring findings suggestive of benign Adrenal Mass
   1. No history of other malignancy (lowers risk to 0.3% chance of cancer)
   2. Reassuring imaging findings suggestive of benign mass
      1. Lesions smaller than 4 cm with smooth borders
      2. Lipid-containing lesions
         1. CT with low attenuation (<10 Hounsfield Units) homogeneous mass
         2. MRI with signal loss on out-of-phase imaging
      3. Rapid-washout of IV iodinated contrast
6. Indications: Follow-up Imaging
   1. Distinguish benign Lesions versus cancer
   2. Distinguish functioning versus non-functioning
7. Evaluation: Protocol
   1. Adrenal Mass on CT Scan <1 cm in greatest diameter
      1. No further evaluation needed
   2. Adrenal Mass on CT Scan >4 cm in greatest diameter
      1. Evaluate endocrine labs above (especially to rule out Pheochromocytoma)
      2. Refer to surgery for removal
   3. Adrenal Mass 1-4 cm and lipid containing lesion on initial imaging (see above)
      1. Consider evaluating endocrine labs above (especially to rule out Pheochromocytoma)
      2. Repeat unenhanced CT Abdomen in 12 months to confirm no change
   4. Adrenal Mass 1-4 cm and not a lipid containing lesion
      1. Evaluate endocrine labs above (especially to rule out Pheochromocytoma)
      2. Perform CT Abdomen with IV contrast and delayed phase (or MRI as alternative)
      3. If CT or MRI non-diagnostic, consider FDG-PET
      4. Referral
         1. Endocrinology for functional adenomas
         2. General surgery for suspicious or non-diagnostic imaging
8. References
   1. Cook (1996) Am J Med 101:88-94
   2. Grumbach (2003) Ann Intern Med 138:424-9
   3. Higgins (2001) Am Fam Physician 63:288-99
   4. Yoh (2008) Ann Nucl Med 22(6): 513-9
   5. Young (2007) N Engl J Med 356(6): 601-10
   6. Willatt (2010) Am Fam Physician 81(11): 1361-6