EUS in the evaluation of pancreatic cystic lesions

Background: The differential diagnosis in pancreatic cystic lesions is often difficult despite the availability of various modern imaging modalities. This study assessed the role of EUS in the following: (1) discrimination of pseudocysts from pancreatic cystic tumors, (2) differential diagnosis between serous cystadenoma and mucinous cystic tumor, and (3) prediction of accompanying malignancy in intraductal papillary mucinous tumor. Methods: EUS findings in 75 patients with pancreatic cystic lesions (58 cystic tumors, 17 pseudocysts) were evaluated. In the comparison of pseudocysts and cystic tumors, the latter included intraductal papillary mucinous tumor, mucinous cystic tumors, and serous cystadenomas, but not solid-pseudopapillary tumors. Results: In univariate analysis, pseudocysts exhibited echogenic debris and parenchymal changes more often than cystic tumors did (respectively, 29% vs. 6%, p < 0.05; and 65% vs. 4%, p < 0.001). In contrast, septa and mural nodules were found more frequently in cystic tumors than pseudocysts (respectively, 69% vs. 12%, p < 0.001; 56% vs. 12%, p < 0.01). Multivariate analysis revealed that parenchymal changes (odds ratio [OR] = 83.59; p < 0.01); septa (OR = 30.75; p < 0.05); and mural nodules (OR = 21.38; p < 0.05) were independent predictors of differentiation between pseudocysts and cystic tumors. Serous cystadenoma exhibited diverse EUS features, as well as a honeycomb appearance. Mural nodules were found more often in mucinous cystic tumors than in serous cystadenomas (p < 0.05). There were no factors that predicted malignancy in intraductal papillary mucinous tumor. Conclusions: EUS is a useful complementary imaging method for differentiation of pancreatic cystic lesions.