“ If there is malignancy elsewhere, there is up to a 50% risk of the nodule being a metastasis. Masses >4 cm may be resected, while benig...
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If there is malignancy elsewhere, there is up to a 50% risk of the nodule being a metastasis. Masses >4 cm may be resected, while benign-appearing lesions <1 cm do not require follow-up.
CT
• HU <10 (lipid rich) is an adenoma; if HU >10 (lipid poor), then the lesion is indeterminate so proceed with contrast.
• Dedicated adrenal assessment with a triple-phase (pre- and post-contrast, then delayed at 15 minutes) scan to allow you to calculate the absolute percentage washout (APW)
• APW = ([HU enhanced – HU delayed]/[HU enhanced – HU unenhanced]). Use thin slices and region of interest (ROI) >50% of the size of the nodule.
• APW >60% = likely adenoma (i.e. rapid enhancement and washout)
• APW <60% and delayed HU >35 = indeterminate—could be a metastasis!
These patients may get a biopsy if there is a history of malignancy or it is a new mass; otherwise, follow-up is recommended.
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