Which one of the following is not a CT feature of Adrenal adenoma?

Enhances rapidly, contrast stays in it for relatively longer time and washes out late Adrenal adenomas show rapid contrast enhancement and rapid subsequent washout; whereas nonadenomas (adrenal ca, mets and pheochromocytomas) show slower washout. Characterstics of adenomas (which help differentiate it from nonadenomas) Homogenous well defined rounded tumor; usually smaller than 4 cm Low attenuation on CT Signal loss on MR chemical shift imaging Contrast enhancement pattern (adenomas show rapid enhancement and rapid washout whereas nonadenomas show delayed washout) Findings s/o malignancy in an incidentally discovered adrenal mass (Harrison 17/e p2258) - large size >4 cm - tumor inhomogenesity and irregular margins - calcifications - high attenuation of CT - no loss of signal on Chemical shift MR