Continuous and progressive 'wash-in' without 'wash-out' of contrast in adrenal mass: a useful feature of ganglioneuroma.

Computed tomography (CT) scan is a useful and widely performed diagnostic modality to evaluate adrenal masses. Nature of the mass determines the degree of attenuation both in unenhanced and in different phases of contrast enhancement. Benign neurogenic tumours like ganglioneuroma mimicks pheochromocytoma and adrenocortical carcinoma in non-contrast CT scan. The 'adrenal protocol' routinely calculates the wash-out pattern at delayed venous phase (DVP) (15 min) following contrast administration to differentiate majority of benign masses from the malignant ones. Ganglioneuromas typically exhibit continuous wash-in of contrast where enhancement gradually increases to attain its peak in DVP. Such wash-in pattern is different from the wash-out pattern observed in pheochromocytomas or adrenocortical adenomas or carcinomas. Presence of this wash-in pattern provides a useful clue to the clinician for underlying ganglioneuroma in hormonally inactive adrenal masses with suspicious morphological appearances. This wash-in pattern also effectively rules out any malignant potential of ganglioneuroma, and thus helps in preoperative decision-making.