What is the management approach for an adrenal gland lesion with a Hounsfield unit (HU) of 76?

Management of Adrenal Lesion with 76 Hounsfield Units

An adrenal mass measuring 76 HU on unenhanced CT is highly suspicious for malignancy and requires immediate surgical evaluation, comprehensive hormonal workup, and staging imaging to assess for metastatic disease. 1

Why This HU Value is Concerning

• Hounsfield units >20 carry a significantly elevated risk of malignancy (6.3% risk), while HU >10 excludes the diagnosis of a benign lipid-rich adenoma. 1 At 76 HU, this lesion falls well above all benign thresholds and demands aggressive evaluation.

• The established threshold of ≤10 HU on unenhanced CT has 100% specificity for benign adenomas, meaning any value above this—especially one as high as 76 HU—cannot be confidently classified as benign. 1

• Lesions with HU >20 that are inhomogeneous warrant surgical intervention as the usual management choice due to sufficient malignancy risk. 2

Immediate Diagnostic Workup Required

Hormonal Evaluation (Must Be Completed Before Any Intervention)

All patients require screening for pheochromocytoma before any surgical or biopsy procedure to prevent life-threatening hypertensive crisis: 1

• Measure plasma-free or 24-hour urinary fractionated metanephrines immediately 1
• Consider plasma methoxytyramine if available, as this biomarker helps assess likelihood of malignancy in pheochromocytomas 1

Screen for autonomous cortisol secretion: 1

• Perform 1 mg overnight dexamethasone suppression test (cortisol >138 nmol/L or >5.0 μg/dL indicates hypersecretion) 3, 2

If hypertension or hypokalemia present: 1

• Measure aldosterone-to-renin ratio (ratio >20 ng/dL per ng/mL/hr suggests hyperaldosteronism) 3

Assess for virilization or suspected adrenocortical carcinoma: 1

• Measure serum DHEA-S, testosterone, and androstenedione 1

Staging Imaging

Obtain cross-sectional imaging of chest, abdomen, and pelvis with IV contrast to evaluate for: 1

• Local invasion or tumor extension into inferior vena cava
• Lymph node involvement
• Distant metastases (lung, liver are most common sites) 1

Consider FDG-PET/CT for indeterminate lesions, as malignant adrenal masses typically show high FDG uptake. 1, 4

Surgical Management Decision

Multidisciplinary review by endocrinology, surgery, and radiology is mandatory before proceeding. 1

If Suspected Adrenocortical Carcinoma:

• Minimally invasive adrenalectomy can be offered only if the tumor can be safely resected without capsular rupture. 1
• Open adrenalectomy should be performed for larger tumors, locally advanced disease, lymph node metastases, or tumor thrombus. 1
• En bloc resection with negative margins is critical for oncologic outcomes 1

If Pheochromocytoma Confirmed:

• Adrenalectomy is indicated, with minimally invasive surgery preferred when feasible. 1
• Preoperative alpha-blockade (typically phenoxybenzamine) for 10-14 days is essential before surgery 1

If Functional Cortical Tumor:

• Unilateral adrenalectomy of the affected gland is indicated, with MIS preferred when feasible. 1

Critical Pitfalls to Avoid

• Never perform biopsy before excluding pheochromocytoma—this can precipitate fatal hypertensive crisis. 1
• Do not use size alone to determine malignancy risk; a small lesion with high HU can still be malignant. 1
• Avoid assuming metastatic disease without tissue diagnosis if patient has known extra-adrenal malignancy—primary adrenal malignancies can coexist. 5
• Do not delay surgical referral for lesions with HU >20 and concerning features, as adrenocortical carcinomas have poor prognosis when diagnosis is delayed. 1, 2

If Biopsy Considered

Biopsy should NOT be performed routinely and is only justified when: 1

• Patient has known extra-adrenal malignancy AND
• Diagnosis of adrenal metastasis would change management AND
• Pheochromocytoma has been definitively excluded 1

Fine needle aspiration carries risk of tumor spill for adrenocortical carcinoma and is contraindicated in suspected pheochromocytoma. 1