Abstract
Adrenocorticotropic hormone (ACTH)-independent hypercortisolism accounts for 15%-20% of cases of Cushing syndrome and always arises from primary adrenal disease. Computed tomographic (CT) and magnetic resonance (MR) imaging findings in 37 patients with primary adrenal Cushing syndrome were analyzed and correlated with pathologic findings. Hyperfunctioning adenomas (n = 24), together with functioning carcinomas (n = 10), accounted for 92% of cases. Adenomas had a significantly smaller mean size (3.5 vs 14.5 cm) and lower mean unenhanced CT attenuation value (11 vs 28 HU) than did carcinomas. The presence of necrosis, hemorrhage, and calcification favored a diagnosis of carcinoma. Six of 10 carcinoma patients had metastases at presentation. Two adenomas were seen within a myelolipoma, which was recognized at both CT and MR imaging due to its fat content, and two adenomas were of uncertain malignant potential. Bilateral disease--primary pigmented nodular adrenal dysplasia (PPNAD) (n = 2) and ACTH-independent macronodular adrenal hyperplasia (AIMAH) (n = 1)--had characteristic imaging features. In PPNAD, multiple tiny (2-5-mm) nodules were visible bilaterally, with no overall glandular enlargement and normal intervening adrenal tissue. In AIMAH, both glands were grossly enlarged and contained nodules up to 3 cm in diameter. Familiarity with the range of imaging appearances of the adrenal glands in primary adrenal Cushing syndrome may help establish the underlying diagnosis.
Highlights
Cushing syndrome is the clinical manifestation of hypercortisolism and is most frequently iatrogenic
ACTHindependent Cushing syndrome is due to an adenoma or carcinoma in the majority of cases but on rare occasions may be caused by other diseases, including primary pigmented nodular adrenal dysplasia (PPNAD) and adrenocorticotropic hormone (ACTH)-independent macronodular hyperplasia (AIMAH) [3,4]
We describe the range of imaging appearances of primary adrenal diseases that can cause ACTH-independent Cushing syndrome
Summary
Cushing syndrome is the clinical manifestation of hypercortisolism and is most frequently iatrogenic. Endogenous Cushing syndrome is a relatively rare disease and may be adrenocorticotropic hormone (ACTH)– dependent (80%– 85% of cases) or ACTH-independent (15%–20%) [1]. ACTH-dependent Cushing syndrome is due to an ACTH-secreting pituitary adenoma (Cushing disease) in approximately 75%– 85% of cases. An ectopic source of ACTH may cause ACTH-dependent Cushing syndrome [1,2]. ACTH-independent Cushing syndrome is always caused by primary adrenal disease [1]. The hyperfunctioning primary adrenal disease secretes cortisol and results in Cushing syndrome. ACTHindependent Cushing syndrome is due to an adenoma or carcinoma in the majority of cases but on rare occasions may be caused by other diseases, including primary pigmented nodular adrenal dysplasia (PPNAD) and ACTH-independent macronodular hyperplasia (AIMAH) [3,4]. There are no large series describing the imaging features of ACTH-independent Cushing syndrome
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