What is the best treatment approach for an adult patient with a non-functional adrenal adenoma with features of myelolipoma that has doubled in size over the past 8 years?

Management of Growing Adrenal Myelolipoma

For a non-functional adrenal adenoma with myelolipoma features that has doubled in size over 8 years, you should proceed with adrenalectomy given the significant growth rate (>5 mm/year threshold), the need to exclude malignancy in an atypical presentation, and the current size likely exceeding 4 cm. 1

Why Surgery is Indicated in This Case

This case presents an unusual clinical scenario that deviates from typical myelolipoma behavior and warrants surgical intervention for several reasons:

Growth Rate Exceeds Guideline Thresholds

• Adrenalectomy should be considered for adrenal incidentalomas growing >5 mm/year after repeating functional work-up. 1
• Doubling in size over 8 years represents substantial growth that exceeds the 3 mm/year threshold where no further follow-up is needed 1
• A recent study from a tertiary referral center found the mean growth rate of observed myelolipomas was only 0.13 cm/year, making your patient's growth rate highly atypical 2

Atypical Presentation Raises Diagnostic Uncertainty

• While myelolipomas are definitively benign with no malignant potential when correctly diagnosed 3, significant growth over time is unusual and raises concern about the accuracy of the initial diagnosis 4
• Very large myelolipomas can be confused with necrotic adrenal carcinomas, necessitating surgical removal for definitive diagnosis 4
• Surgery plays an important role for lesions that cannot be distinguished reliably from malignancy 5

Size Considerations

• If the lesion has doubled in size over 8 years, it likely now exceeds 4 cm (the threshold where repeat imaging is recommended even for radiologically benign lesions) 1, 6
• Patients with non-functional adrenal lesions that are radiologically benign but ≥4 cm should undergo repeat imaging in 6-12 months, and surgery should be considered if growth continues 1

Pre-Operative Requirements

Before proceeding to surgery, you must:

Repeat Functional Work-Up

• Perform complete hormonal evaluation including screening for pheochromocytoma (plasma metanephrines), Cushing's syndrome (1 mg dexamethasone suppression test or 24-hour urinary free cortisol), and if hypertensive or hypokalemic, primary aldosteronism (plasma aldosterone-renin ratio) 6
• This is critical because approximately 5% of radiologically benign incidentalomas have subclinical hormone production requiring treatment 6
• The guideline specifically states to repeat functional work-up before considering adrenalectomy for growing lesions 1

Confirm Imaging Characteristics

• Verify the lesion still demonstrates macroscopic fat on current imaging (CT showing negative Hounsfield units in fat-containing areas) 3
• If imaging characteristics have changed or become indeterminate, this further supports surgical intervention 2

Surgical Approach

Laparoscopic Adrenalectomy is Preferred

• Minimally invasive surgery (laparoscopic or retroperitoneoscopic) should be performed when feasible for benign lesions 7
• Laparoscopic adrenalectomy for myelolipomas has comparable outcomes and morbidity to other adrenal pathology, even for large lesions 8
• In a series of 15 laparoscopic adrenalectomies for myelolipomas (mean size 8.4 cm), outcomes were excellent with minimal morbidity 8

Consider Open Approach for Very Large Lesions

• The European Society of Endocrinology suggests 6 cm as a cutoff for considering open rather than laparoscopic adrenalectomy 1, 7
• One case report described successful open adrenalectomy for a 21-cm myelolipoma 8

Common Pitfalls to Avoid

• Do not continue surveillance indefinitely for a growing lesion. While surveillance is safe for stable myelolipomas 2, continued growth mandates intervention 1
• Do not perform adrenal biopsy. The diagnosis should be made based on imaging characteristics and confirmed at surgery 6
• Do not assume the lesion is benign based solely on fat content. Atypical growth patterns warrant histologic confirmation 5, 4
• Do not proceed to surgery without repeating hormonal evaluation. Undiagnosed pheochromocytoma can cause intraoperative hypertensive crisis 6

Expected Benefits of Surgery

Surgery in this case is both diagnostic and therapeutic:

• Provides definitive histologic diagnosis to exclude malignancy 5
• Prevents potential complications such as spontaneous rupture and hemorrhage, which can lead to cardiovascular shock 5
• Addresses any mass effect on adjacent organs if present 2
• Provides symptom relief if the patient has developed abdominal or flank pain 8, 9