Imaging of adrenocortical cancer
Adrenocortical cancer (ACC) is a rare and challenging malignancy for clinicians. The cornerstone of imaging for the diagnosis of ACC or re-evaluation of known ACC is thin-collimation computed tomography (CT) without contrast and after early and late washout of contrast medium. Although size and shape of adrenal lesions must be taken into consideration to differentiate adenomas from other adrenal lesions, it is pre- and post-contrast adrenal lesion density, measured in Hounsefield units, which is the key parameter not to be omitted; histogram analysis is also useful (sensitivities of 6798% and specificity of 100% have been reported for both modalities). Chest CT is useful for staging while CT angiography gives important information on tumor extension. Multiplanar magnetic resonance imaging (MRI) is helpful, particularly in delineating tumor vascular extension. MRI refinements such as chemical shift add to its diagnostic potential (with sensitivity of 79100% and specificity of 94100%). Approximately one third of adrenal lesions cannot initially be categorized with CT/MRI. Functional (i.e. nuclear medicine) modalities are used to further evaluate patients. 131I-iodonorcholesterol (NP-59) imaging is an adrenal-cortex-specific modality, with sensitivity of 79%, but its availability is limited. Positron-emission tomography (PET) with 11C-metomidate is a recent adrenal-cortex-specific modality giving good results but its availability is also limited due to the very short half-life of 11C (newer relevant clinical studies are being undertaken with radionuclides that have a longer half-life). PET with 18F-fluorodeoxyglucose (FDG) may be non-specific for the adrenal cortex but its wide availability (and the combination of PET/CT) has yielded extensive and useful information on the evaluation of adrenal and extra-adrenal lesions. Bone scintigraphy can detect osseous disease extension. The use of CT plus FDG PET/CT may be time-saving, if not cost-effective, in the evaluation of ACC (with sensitivity of 97% and specificity of 91%).
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.