Does a 3.5 cm benign adrenal adenoma that grew 1 cm over 8 years require surgical intervention?

Management of a 3.5 cm Benign Adrenal Adenoma with 1 cm Growth Over 8 Years

This adenoma requires surgical resection because its growth rate of 1.25 mm/year, while slow, exceeds the threshold for continued observation and the lesion now measures 4.5 cm, which mandates consideration for adrenalectomy. 1

Growth Rate Analysis

The growth rate of this lesion is approximately 1.25 mm/year (10 mm over 8 years), which falls into a critical decision zone:

• Growth <3 mm/year typically requires no further intervention according to current guidelines 1, 2
• Growth >5 mm/year mandates consideration of adrenalectomy after repeating functional workup 1, 2
• This lesion's growth rate of 1.25 mm/year is below the 3 mm/year threshold that would automatically trigger surgery 1

However, the absolute size now matters more than growth rate in this case.

Size-Based Surgical Indications

The current size of 4.5 cm (3.5 cm + 1 cm growth) is the critical factor:

• Lesions ≥4 cm require repeat imaging at 6-12 months due to higher malignancy risk, even if benign-appearing 1, 2
• Malignancy should be suspected in nonfunctioning tumors larger than 4 cm with irregular margins or internal heterogeneity 1
• The malignancy risk increases significantly at 4 cm, with most surgically resected adrenocortical carcinomas measuring >4 cm at diagnosis 2, 3
• In patients without history of malignancy, all malignant lesions were greater than 5 cm, but the 4 cm threshold represents an important surveillance point 1

Required Pre-Surgical Workup

Before proceeding with surgery, repeat the complete functional evaluation to exclude hormone hypersecretion that has developed during the observation period:

• Screen for autonomous cortisol secretion with 1 mg dexamethasone suppression test 1, 2
• Screen for pheochromocytoma with plasma or 24-hour urinary metanephrines (mandatory before any surgical consideration) 1, 2
• Screen for primary aldosteronism if hypertensive or hypokalemic with aldosterone-to-renin ratio 1, 2
• Approximately 5% of radiologically benign lesions harbor subclinical hormone production requiring treatment 2, 3

Imaging Reassessment

Obtain updated imaging to confirm benign characteristics before surgery:

• If the lesion demonstrates <10 Hounsfield units on non-contrast CT, it remains consistent with a lipid-rich adenoma 1
• If HU >10, perform chemical shift MRI or washout CT to exclude malignancy 1, 4
• Assess for irregular margins, heterogeneity, or local invasion that would suggest adrenocortical carcinoma 1

Surgical Approach

Minimally invasive adrenalectomy should be performed when feasible for this size lesion:

• Laparoscopic adrenalectomy is appropriate if the tumor can be safely resected without rupturing the capsule 1
• Open adrenalectomy should be considered if imaging suggests malignancy (irregular margins, heterogeneity, local invasion) 1
• The risk of malignancy increases with size, making surgical intervention prudent at 4.5 cm 2, 3

Critical Pitfalls to Avoid

• Never skip pheochromocytoma screening before surgery, as undiagnosed pheochromocytoma can cause life-threatening intraoperative hypertensive crisis 2
• Do not perform adrenal biopsy as part of workup due to limited clinical value and risks including tumor seeding 2, 3
• Avoid laparoscopic approach if imaging suggests adrenocortical carcinoma (large, invasive, heterogeneous), as open surgery is required to prevent carcinomatosis 2

Rationale for Surgery Despite Slow Growth

While the growth rate of 1.25 mm/year is reassuring (all malignant nodules in one study grew >5 mm/year) 5, the absolute size of 4.5 cm crosses the threshold where observation alone is no longer recommended 1, 2, 3. The combination of documented growth (even if slow) and size ≥4 cm justifies surgical intervention to prevent potential malignant transformation and ensure definitive diagnosis.