Adrenal Metastases

The suprarenal glands are two small flattened bodies of a yellowish color, situated at the back part of the abdomen, behind the peritoneum, and immediately above and in front of the upper end of each kidney; hence their name. The right one is somewhat triangular in shape, bearing a resemblance to a cocked hat; the left is more semilunar, usually larger, and placed at a higher level than the right. They vary in size in different individuals, being sometimes so small as to be scarcely detected: their usual size is from 3 to 5 cm. in length, rather less in width, and from 4 to 6 mm. in thickness. Their average weight is from 1.5 to 2.5 gm. each.

The adrenal gland is a common site of metastatic disease. Modern cross-sectional imaging (CT and MRI) reveal that adrenal metastases occur more frequently than previously believed.

Adrenal metastases may be unilateral or bilateral. The tumors vary in size. Central necrosis and hemorrhage may occur, but calcification is rare. Palliative radiation is useful for adrenal mets if they are painful (see studies below). Surgery may be curative if the adrenal gland is the only site of spread (go here).

The adrenal glands are the fourth most common site of metastasis after the lungs, liver, and bone. The most common primary sites are lung, breast, skin (melanoma), kidney, thyroid, and colon cancers. The reported frequency of adrenal metastases depends on the incidence of the primary tumor; however, for each primary malignancy, the frequency of adrenal metastases is different. Some malignancies are more likely to have adrenal metastases. About 50% of melanomas metastasize to the adrenal glands, and 30-40% of breast and lung cancers and 10-20% of renal and gastrointestinal tumors have adrenal metastases.

The imaging phenotype of metastases to the adrenal gland of non-adrenal primary malignancy includes:

  • Irregular shape and inhomogeneous nature
  • Tendency to be bilateral
  • High unenhanced CT attenuation values (>10 HU) and enhancement with intravenous contrast on CT (>40 HU at 30 min after contrast administration)
  • Isointensity or slightly less intense than the liver on T-1 weighted MRI and high to intermediate signal intensity on T-2 weighted MRI (representing an increased water content)