What is the diagnostic approach for suspected adrenal tumor?

Diagnostic Approach for Suspected Adrenal Tumor

All patients with suspected adrenal tumors require both comprehensive hormonal evaluation and cross-sectional imaging with unenhanced CT as the first-line diagnostic approach. 1, 2

Initial Hormonal Evaluation (Mandatory for All Patients)

Complete hormonal screening must be performed before any surgical intervention, regardless of tumor appearance on imaging, as radiological characteristics cannot reliably predict hormone secretion status. 2

Required Hormone Tests

Cortisol excess screening:

• 1 mg overnight dexamethasone suppression test (preferred screening method) 1, 2
• Basal plasma ACTH levels 1, 2
• 24-hour urinary free cortisol 1
• Basal serum cortisol 1

Aldosterone excess screening (if hypertension and/or hypokalemia present):

• Aldosterone-to-renin ratio 1, 2
• Serum potassium 1

Catecholamine excess screening:

• Plasma free metanephrines (normetanephrine, metanephrine, methoxytyramine) - preferred test 1, 3
• Alternative: 24-hour urinary fractionated metanephrines 1
• Critical exception: Skip catecholamine testing ONLY if unenhanced CT shows unequivocal adenoma with <10 HU AND patient has no adrenergic symptoms 1

Androgen/sex steroid excess (if virilization or suspected adrenocortical carcinoma):

• DHEA-S 1, 2
• 17-OH-progesterone 1
• Androstenedione 1
• Testosterone 1
• 17-beta-estradiol (in men and postmenopausal women) 1

Imaging Evaluation

First-Line Imaging

Unenhanced (non-contrast) CT of the abdomen is the mandatory first imaging study for all adrenal masses. 1, 4 This provides critical diagnostic information:

• Hounsfield units (HU) <10: Strongly suggests benign adenoma 1
• HU >10: Requires further evaluation with second-line imaging or functional imaging 1

Chest CT should be obtained concurrently to evaluate for metastatic disease. 1

Second-Line Imaging (for Indeterminate Masses)

When unenhanced CT shows HU >10, proceed with either:

• Contrast-enhanced CT with 15-minute delayed washout imaging 1
• Chemical-shift MRI 1

MRI is preferred over CT when pheochromocytoma is suspected due to risk of hypertensive crisis with IV contrast administration. 1, 5

Advanced Functional Imaging

FDG-PET is indicated for:

• Radiologically indeterminate lesions after second-line imaging 1
• Suspected adrenocortical carcinoma 1
• Established pheochromocytoma (FDG-PET is superior to MIBG), particularly with SDHB mutation or suspected malignancy 1, 5

Additional functional imaging options for pheochromocytoma:

• MIBG scintigraphy 1
• DOTA-TATE-PET 1
• Dopa/Dopamine PET 1

Critical Diagnostic Pitfalls to Avoid

Never perform fine needle biopsy of a suspected adrenal tumor before excluding pheochromocytoma biochemically - this can trigger fatal hypertensive crisis. 1, 5, 3 Biopsy is almost never justified for suspected adrenocortical carcinoma due to risk of tumor spill. 1

Do not skip hormonal evaluation even in apparently "benign-appearing" tumors on imaging - subtle hormone production impacts surgical management and perioperative care. 2

Do not rely solely on imaging characteristics to determine hormone secretion status - biochemical testing is mandatory. 2

When to Involve Multidisciplinary Team

Immediate multidisciplinary review (endocrinology, surgery, radiology) is required when: 1

• Imaging is not consistent with benign lesion
• Evidence of hormone hypersecretion detected
• Tumor has grown significantly on follow-up
• Adrenal surgery is being considered

Special Considerations for Specific Tumor Types

For suspected adrenocortical carcinoma:

• Bone scintigraphy if skeletal metastases suspected 1
• FDG-PET optional but useful 1
• Pathological diagnosis requires experienced pathologist using Weiss score (≥3 suggests malignancy) 1

For confirmed pheochromocytoma:

• Extend imaging to chest and neck if initial abdominal imaging negative but biochemistry positive 5, 3
• Consider genetic testing (>35% have germline mutations) 6
• Lifelong surveillance required due to malignancy risk 1, 3