Endocrine: Adrenal Incidentaloma

Definition

• Asymptomatic Adrenal Mass Incidentally Found on Radiographic Examination

Causes

• Nonfunctional Benign Tumor (85-90%)
  • Cortical Adenoma (Most Common)
  • Ganglioneuroma
  • Myelolipoma
  • Adrenal Cyst
• Functional Benign Tumor (10-15%)
  • Aldosteronoma
  • Cortisol-Secreting Adenoma
  • Pheochromocytoma
• Malignancy (2-5%)
  • Adrenocortical Carcinoma
  • Metastases (Most Common Primary Sites: Lung #1, Breast, Melanoma & Kidney)

Management

• Always Start with Thorough History & Physical Exam
• First Step: Assess Hormonal Function
• Second Step: Assess Risk of Malignancy
• Third Step: Determination of Treatment

Assessment of Hormonal Function

• Plasma Aldosterone & Renin – Evaluate for Hyperaldosteronism (Conn Syndrome)
• 24-Hour Urinary Cortisol or Low-Dose Dexamethasone Suppression Test – Evaluate for Hypercortisolism (Cushing Syndrome)
• Plasma or Urine Metanephrines – Evaluate for Pheochromocytoma

Assessment of Malignancy Risk

• Benign CT Findings:
  • Size < 4 cm
  • Homogenous
  • Precontrast Density < 10 Hounsfield Units (HU)
  • Contrast Washout > 50% at 10 Minutes
• Malignant CT Findings:
  • Size > 6 cm
  • Heterogenous
  • Precontrast Density > 20 Hounsfield Units (HU)
  • Delayed Contrast Washout
• FNA Biopsy Generally Not Preformed
  • Cannot Distinguish Benign Mass from Carcinoma & May Increase Difficulty of Adrenalectomy
  • May Be Useful in Distinguishing a Metastatic Tumor – Although Pheochromocytoma Must Always be Ruled Out Prior to Biopsy

Treatment

• Non-Functioning & Benign CT Findings: Observe
  • Repeat CT in 3-6 Months, Then Annually for 1-2 Years
  • Repeat Biochemical Testing Annually for 5 Years
• Functioning or Malignant CT Findings: Adrenalectomy
  • *See Endocrine: Adrenalectomy
  • Surgery Indications:
    • Hormonally Functional
    • Size > 4-6 cm or Rapid Growth
    • Known/Suspected Adrenocortical Carcinoma
    • Metastatic Tumors
  • Approach:
    • Laparoscopic Adrenalectomy is Preferred if Able
    • Open (Anterior/Transabdominal) Approach if Large > 6 cm or Known/Highly-Suspected Adrenocortical Carcinoma
• *Treatment for Size 4-6 cm is Controversial

Myelolipoma

• Benign Tumor of Adipose & Myeloid Tissue
• Rare Outside of the Adrenal Gland
• Compromise 6-16% of Adrenal Incidentalomas
• Characteristic CT Findings: Well Circumscribed & Hypodense with Attenuation -90 to -120 HU
• Traditionally Treated Conservatively
  • Indications for Adrenalectomy: Symptomatic or Large (> 6 cm)