Adrenal lesions

Adrenal incidentaloma

• Most common lesion to be incidentally found - about 1% of patients have one, mostly these are non-functioning
• Uncommon in patients <40yo
• In patients with a history of malignancy, metastatic disease is most likely, especially when bilateral
• Only investigate if >1cm in size?

Differential diagnosis

• • Functioning
    • Phaeochromocytoma
      • See separate topic
    • Cortisol-producing adrenoma/subclinical Cushing's syndrome
      • See separate topic ('hypercortisolism')
    • Aldosteronoma (aldosterone producing adenoma)
      • See separate topic 'hyperaldosteronism' for complete guidelines
      • Less likely to be seen as incidentaloma, as these are generally small
      • Suspect in any patient hypertensive and hypokalaemic
    • Primary adrenal hyperplasia
  • Non-functioning
    • Non-functioning cortical adenoma
      • By far most common incidentaloma
      • Diagnosis
        • Consistent imaging appearance and negative biochemical evaluation
        • Two types on CT:
          • Lipid-rich adenoma (HU <=10): these are the only adrenal incidentals with such low attenuation and only requires further imaging if there are other concerning features such as size >4cm. There is good data to say the sensitivity is as high as 100% for significant lesions if HU <=10.
          • Lipid-poor adenoma (HU >10): need to carefully exclude differentials
      • Treatment
        • Adrenalectomy if >4cm or with imaging characteristics atypical for adenoma
    • Myelolipoma
      • Benign adrenal lesions made up of fat and bone marrow elements
      • Can grow up to 15cm and can be bilateral
      • Diagnosed based on presence of macroscopic fat on CT/MRI (don't even need to measure HU because it clearly just looks like fat)
      • Usually asymptomatic
      • Should not be removed unless atypical appearance or suspected to be causing local symptoms
    • Adrenal haemorrhage
      • Can occur from trauma or spontaneous if anticoagulated, especially in the setting of adrenal tumour
      • Waterhouse-Friderichsen syndrome - adrenal insufficiency from atraumatic haemorrhage in the setting of septicaemia
      • Diagnosed on imaging
      • Serial imaging - repeat 3-6 months if felt to be most likely diagnosis
      • In most cases, won't require adrenalectomy
    • Adrenal cyst
      • May be endothelial cysts or pseudocysts from prior haemorrhage or infarction
      • Usually readily recognisable, although there may be evidence of haemorrhage within them
      • Only require surgery if they are large and patient is having symptoms
    • Ganglioneuroma
      • Benign tumours arising from sympathetic nerve fibres that can be immediately adjacent to adrenal gland
      • Not functionally active
      • Remove only if diagnosis uncertain
    • Infection
  • Malignant
    • Adrenocortical carcinoma
      • See separate topic
      • About 10% of adrenal incidentalomas turn out to be these
        • <4cm = 2%
        • 4-6cm = 6%
        • >6cm = 25%
      • Usually large (>6cm)
    • Metastases to the adrenal gland

Approach to workup

1. Verify that the lesion is in the adrenal gland
2. Determine if the lesion is hypersecreting adrenal hormones
3. Assess whether it is potentially malignant
4. Assess whether there are any compressive symptoms

Workup:

• History - HTN, spells (headaches, palps, anxiety), weight gain, hypokalaemia, other cancer
• Screening - as per algorithm below for ALL patients
  • FBE/UEC/LFT/CMP
  • 1mg DMST then ACTH if abnormal
  • Plasma renin and aldosterone
  • If HU>=10: plasma metanephrines and normetanephrines, then if positive do a 24 hour urine collection
  • If checking for sex steroid lesions (which is routinely done, but a selective approach would also be justified), send 24-hour urine testosterone, DHEA, and DHEA-S or serum DHEAS
  • Imaging of adrenals
• If initial study was an USS, need a CT (or MRI if suspected phaeochromocytoma)
  • Dedicated adrenal CT has a non-con, arterial, PV and delayed phase
    • <10HU is extremely reassuring
    • Benign if >60% absolute washout or >40% relative washout
    • Concerning if irregular borders, heterogenous (haemorrhage/necrosis), invasion, mets, growth
  • FDG PET is good at distinguishing benign and malignant
• Percutaneous biopsy is not good
  • Primary adrenal malignancy cannot be diagnosed on cytologic criteria
  • ACC can be seeded with biopsy
  • Must exclude phaeo first - can cause adrenergic crisis
  • Sometimes used to diagnose mets

Usual approach to management:

• No concern. Any size and homogenous and HU <10: lipid-rich adenoma, no further imaging required
• Low concern. <4cm and homogenous and HU 11-20: follow-up for 1-2 years
• Moderate concern. HU 11-20 and >4cm, or homogenous HU >20 and <4cm, or heterogenous <4cm: close follow-up vs surgery depending on MDM.
• High concern. >4cm and HU >20: immediate surgery.

Indications for resection:

• Hormonally active
• Concerning for malignancy (according to American Association of Clinical Endocrinologists, any lesion with concerning radiographic characteristics as well as most lesions 4cm or larger should be resected because of increased cancer risk - but not including myelolipomas)
  • Sabiston suggests remove all >4cm in fit patients, since CT/MRI underestimate lesion size by 20%
• Relative indications
  • Strongly consider removal of those 3-4cm, especially in young patients
  • Suspicious imaging characteristics, such as heterogeneity, or HU >20
  • Growth on interval imaging
  • Patient preference

Follow-up

• Repeat CT at 6-12 months and then annually for the next 1-2 years for non-op tumours
• Biochemical screening yearly for 5 years
• Consider excision for lesions increasing in size (>1cm over 12 months is a good indication for resection) or that have emerging evidence of hormonal hypersecretion