Which of the following is not a CT feature of adrenal adenoma?

Adrenal adenoma on contrast enhanced CT/MRI show rapid uptake and relatively rapid washout of contrast material than non adenomas. CT Features of Adrenal Adenoma Well defined /sharply defined <5 cm in size Low attenuation (< 10 HU) due to lipid content Mild homogenous enhancement Relatively rapid washout of contrast material (due to lack of large interstitial spaces) Relatively rapid washout is characteristic of adenoma