Adrenal metastases are the most common malignant lesions involving the adrenal gland. Metastases are usually bilateral but may also be unilateral. When unilateral involvement is thought to be more prevalent on the left side (ratio of 1.5:1).
They are thought to be present in up to 27% of patients with known malignant epithelial tumors at autopsy.
Many primary tumors can potentially metastasize to the adrenal glands. Common primary tumors that metastasize to the adrenal glands include:
Other reported primary tumors include:
Adrenal metastases can have a variable CT appearances 4. Usually, demonstrates less than 50% washout.
In patients with renal cell carcinoma and hepatocellular carcinoma who undergo dedicated adrenal CT imaging for known adrenal lesions, the percentage enhancement washout of adrenal metastases can be similar to that of lipid-poor adrenal adenomas. As hypervascular lesions, they commonly show vivid enhancement on the portal venous phase, usually more than 120 HU, and thus can be easily identified.
Exact signal characteristics can vary dependent 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 vivid enhancement of more than 120 HU is identified in the portal venous phase, the washout should be ignored, and an hypervascular lesion such as RCC and HCC metastasis should be considered
- MRI: lack of signal loss on out-of-phase images