When an adrenal mass fails the adenoma tests (unenhanced ≤ 10 HU, washout, signal drop), size, heterogeneity, growth and the clinical picture separate carcinoma, phaeochromocytoma and metastasis — and biochemistry must come before any biopsy.
Orient first
- Adrenocortical carcinoma: large (often > 4–6 cm), heterogeneous, necrotic, calcified, may invade the IVC.
- Phaeochromocytoma: avid enhancement, often very bright on fluid-sensitive MRI, can fail washout criteria; plasma metanephrines must be checked before biopsy or surgery.
- Metastasis: known primary (lung, melanoma, renal), bilateral, growing.
Acquire the study
- Unenhanced, portal venous (60–75 s) and 15-min delayed phases; coronal reformats.
The manoeuvre
- Unenhanced attenuation in HU (≤ 10 HU = lipid-rich adenoma — stop).
- Absolute and relative washout (use the calculator); failing washout keeps malignancy and phaeochromocytoma on the list.
- Size in cm, necrosis, calcification, margins; growth versus prior studies.
- IVC and renal vein invasion; nodes, liver and lung metastases.
What confirms it
- A large, heterogeneous or growing adrenal mass that fails the adenoma criteria, with biochemistry and context.
What licenses you to exclude it
- Unenhanced attenuation ≤ 10 HU or diagnostic washout in a homogeneous nodule means adenoma — stop the work-up.
The classic misread
- Applying washout to a heterogeneous, necrotic mass — washout was validated for homogeneous nodules.