Management of Incidental Adrenal Masses: American College of Radiology white paper

In 2017, the Adrenal Subcommittee of the Incidental Findings Committee of the Incidental Findings Committee of the American College of Radiology published a revised algorithm for the management of incidental adrenal masses in patients who are:

• adults (i.e. 18-year-old or over)
• asymptomatic for adrenal pathology
• referred for imaging for reasons unrelated to adrenal pathology

Summary

1. adrenal masses <1 cm do not require further investigation
2. incidental masses should be categorised according to diagnostic imaging features, mass size, growth (cf. prior imaging if available) and cancer history
3. dedicated adrenal CT is preferred to determine if a 1-4 cm mass, with density >10 HU, is a benign adenoma
4. wherever possible, the stability of a lesion should be assessed with any modality that has imaged the adrenals in the past (e.g. chest CT, PET-CT, abdominal US, lumbar spine MRI)
5. consider patients’ co-morbidities, life expectancy and ability to receive treatment before recommending further investigation

The algorithm

Incidental, asymptomatic adrenal mass ≥1 cm

Diagnostic benign imaging features

• myelolipoma or lipid-rich adenoma
  • macroscopic fat
  • density <10 HU on non-contrast CT
  • signal loss compared to the spleen on in-phase and opposed-phase images of a chemical-shift MRI sequence
• cyst
• benign calcified mass e.g. old haematoma or granulomatous infection
• haemorrhage
• normal or benign serum calcium
• no follow-up required

Indeterminate imaging features

Size 1 cm - 4 cm

1. prior imaging

• stable ≥1 year and no biochemical features of functioning adenoma or phaeochromocytoma
  • no follow-up
• new or enlarging
  • no cancer history
    • consider follow-up adrenal CT or resection
  • cancer history
    • consider biopsy or PET-CT

2. no prior imaging, no cancer history

• <2 cm
  • probably benign, consider 12 month adrenal CT
• 2-4 cm
  • adrenal CT

3. no prior imaging, with cancer history and isolated adrenal mass

• adrenal CT

Size >4 cm

• with no cancer history
  • consider resection
• with cancer history
  • consider biopsy or PET-CT

Adrenal CT

• reduced dose non-contrast CT ≤10 HU and no biochemical features of functioning adenoma or phaeochromocytoma
  • benign adenoma, no follow-up
• non-contrast CT >10 HU
  • adrenal CT washout
    1. no enhancement (<10 HU) = cyst or haemorrhage
       • benign, no follow-up
    2. absolute percentage washout (APW) / relative percentage washout (RPW) ≥60/40%
       • and no biochemical features of hyperfunctioning adenoma or phaeochromocytoma
       • benign adenoma, no follow-up
    3. APW/RPW <60/40%
       • imaging follow-up, biopsy, PET-CT or resection depending on clinical scenario