What is the next step for a patient with a left adrenal mass suspicious for malignancy, but with negative urine and plasma tests?

Management of a Left Adrenal Mass Suspicious for Malignancy with Negative Urine and Plasma Tests

For a patient with a left adrenal mass suspicious for malignancy on imaging but negative urine and plasma tests, the next step should be FDG-PET imaging to further characterize the mass before considering adrenal biopsy or surgery. 1, 2

Diagnostic Approach

When faced with an adrenal mass suspicious for malignancy but with negative hormonal workup, the following algorithm should guide management:

1. Confirm completeness of hormonal evaluation

   • Ensure all appropriate hormonal tests were performed:
     • Cortisol (1mg overnight dexamethasone suppression test)
     • Catecholamines (plasma or 24-hour urinary metanephrines)
     • Aldosterone-to-renin ratio (if hypertensive or hypokalemic) 2

2. Review imaging characteristics

   • Size of the mass (masses >5 cm have higher risk of malignancy)
   • Hounsfield units on non-contrast CT (>10 HU suggests non-adenoma)
   • Heterogeneity, irregular margins, and enhancement patterns 1

3. Next imaging step: FDG-PET

   • FDG-PET is particularly valuable for evaluating adrenal masses in the context of suspected malignancy
   • Specific uptake values >4 strongly suggest metastatic disease
   • Values <4 typically indicate benign lesions 1, 3

Management Based on FDG-PET Results

If FDG-PET suggests malignancy (high uptake):

• Surgical consultation for adrenalectomy
  • Minimally invasive approach for smaller, contained masses
  • Open adrenalectomy for larger (>6 cm) or locally advanced tumors 1
  • Preoperative planning should include multidisciplinary discussion 2

If FDG-PET suggests benign lesion (low uptake):

• Follow-up imaging in 3-6 months
  • CT or MRI to assess for growth
  • No further imaging needed if stable and <4 cm 1
  • Consider surgery if growth >5 mm/year is observed 1

Important Considerations

• Avoid adrenal biopsy in potentially resectable adrenal masses as it carries risk of tumor seeding and is contraindicated for suspected adrenocortical carcinoma 1, 2

• Recognize limitations of washout CT: About 1/3 of pheochromocytomas may show washout patterns similar to adenomas, and some malignant masses can mimic benign washout patterns 1

• Be aware that in patients with a history of extra-adrenal malignancy, up to 50% of adrenal masses may be unrelated to the primary cancer (i.e., benign adenomas or other primary adrenal tumors) 4

• Consider chemical shift MRI as an alternative second-line imaging if FDG-PET is unavailable 1, 2

Pitfalls to Avoid

• Don't assume malignancy based solely on size - though size >4 cm increases suspicion
• Don't proceed to biopsy without ruling out pheochromocytoma - can cause life-threatening crisis
• Don't skip FDG-PET in favor of immediate surgery or biopsy for indeterminate masses
• Don't assume metastatic disease in a patient with history of malignancy without appropriate imaging workup

By following this approach, you can systematically evaluate the suspicious adrenal mass and determine the appropriate next steps while minimizing unnecessary procedures and optimizing patient outcomes.