Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. Unilateral involvement is more prevalent on the left side (ratio of 1.5:1).
They are present at autopsy in up to 27% of patients with known malignant epithelial tumors.
Many primary tumors can potentially metastasize to the adrenal glands, commonly:
Other reported primary tumors include:
Adrenal metastases can have a variable CT appearances 4. They usually demonstrate less than 50% washout.
In patients with renal cell carcinoma and hepatocellular carcinoma who undergo dedicated adrenal CT imaging for known adrenal lesions, the enhancement washout of adrenal metastases can be similar to that of lipid-poor adrenal adenomas. As hypervascular lesions, they commonly show intense enhancement on the portal venous phase, usually more than 120 HU, and thus can be easily identified.
Exact signal characteristics can vary depending on the type of tumor. In general, commonly described signal characteristics include:
- T1: usually exhibit low signal intensity 2
- T2: often show high signal intensity 2
- T1 C+ (Gd): usually has progressive enhancement after administration of contrast material 2
An important diagnostic feature is the lack of signal loss on out-of-phase images (in contradistinction to that seen with adrenal adenoma).
- on CT, metastases usually demonstrate less than 50% washout
- if intense enhancement of more than 120 HU is identified in the portal venous phase, washout should be ignored, and a hypervascular lesion such as renal cell carcinoma or hepatocellular carcinoma metastasis should be considered
- MRI: no signal loss on out-of-phase images