Differentiation of pancreatic serous cystadenoma from endocrine tumor and intraductal papillary mucinous neoplasm based on washout pattern on multiphase CT.

Objective: To evaluate the washout (WO) pattern of serous cystadenomas (SCAs) compared with endocrine tumors (ETs) and intraductal papillary mucinous neoplasm (IPMN).

Methods: Patients with serous cystadenoma (n = 12), ET (n = 29), and IPMN (n = 35) underwent 4-phase computed tomography CT. Tumors were categorized as hyperdense or hypodense. Computed tomographic values measured were unenhanced attenuation (AU), pancreatic attenuation (A12, 12 seconds), portal attenuation (A35), and equilibrium (A158). Computed tomographic parameters calculated were wash-in (WI) = A12 - AU; WO = A12 - A35; and washout ratio (WOR) = WO/WI × 100/22.

Results: Hyperdense SCAs had significantly higher WOR than did hyperdense ETs (P = 0.001). Among the 3 hypodense tumors, SCAs had the significantly highest WOR (P < 0.05/3). Relative to the pancreas, the WOR of SCAs were equivalent, whereas the WOR of ETs and IPMNs were significantly lower.

Conclusions: Hyperdense SCAs had significantly higher WOR than did hyperdense ETs, and hypodense SCAs had the significantly highest WOR among the three.