CT features and quantification of the characteristics of adrenocortical carcinomas on unenhanced and contrast-enhanced studies

Abstract

To describe the morphological and contrast-agent washout characteristics of adrenocortical carcinomas (ACCs) on computed tomography (CT). Forty-one patients with histopathologically proven ACCs were retrospectively evaluated. The morphological characteristics of the ACCs were documented and compared with surgical and histopathological findings. The percentage of contrast agent enhancement washout (PEW) and relative PEW (RPEW) were calculated for 17 patients who had the combination of unenhanced, portal venous, and 15 min delayed phase images. Characteristic imaging findings of ACCs included large size (38 of 41 tumours were >6 cm), well-defined margin with a thin enhancing rim (25 patients), and central stellate area of low attenuation on contrast-enhanced CT images (21 patients). Tumour extension into the inferior vena cava (IVC) with associated thrombus was identified on CT in six (14.6%) patients. Of 17 tumours evaluated, 12 (71%) had a PEW value of ≤60%, and 14 (82%) had an RPEW value of ≤40%. Large size, a well-defined margin with a thin enhancing rim, central low attenuation, and a predilection for extension into the IVC are typical morphological characteristics of ACC on CT. The contrast-washout characteristics of ACCs, in concordance with their malignant nature, share those of non-adenomas rather than adenomas.