From needles to numbers: can noninvasive imaging distinguish benign and malignant adrenal lesions?

Adrenal masses are a relatively common finding on computed tomography (CT) and magnetic resonance imaging (MRI). Until recently, adrenal biopsy, resection, or clinical follow-up were the only methods of distinguishing benign adenomas from malignancies. On the basis of their higher lipid content, adenomas have characteristic appearances on CT and MRI that can be used to separate them from non-lipid-containing lesions such as metastases. CT densitometry with or without contrast media and chemical shift MRI (CSI) are two examples of techniques with adequate sensitivity (50-90%) and excellent specificity (> 95%) for adrenal adenomas. While the need for invasive tissue sampling is reduced because of these techniques, it is eliminated because lesions not meeting the criteria for adenomas are not always malignant. However, CT densitometry and CSI are likely to reduce significantly the need for histology sampling of incidentally discovered adrenal masses due to the high specificity of these new techniques.