Can EUS Help Differentiate Macrocystic Serous Cystadenomas from Mucinous Cystadenomas of the Pancreas by Its Morphologic Characteristics?

Background/Aims: Benign pancreatic serous cystadenoma is usually distinguishable from mucinous cystadenoma (MCA), which requires resection because of its malignant potential. Macrocystic serous cystadenoma (M-SCA), a macrocystic variant of serous cystadenoma which is hard to distinguish from MCA, has recently been described. The aim of this study was to describe the morphologic characteristics of M-SCA with EUS, in order to differentiate M-SCA from MCA. Subjects and Methods: Clinical and morphologic characteristics on EUS were reviewed from 31 consecutive patients with M-SCA or MCA who had undergone surgery. Results: Resected specimens were available for 11 M-SCAs and 20 MCAs. Significant differences in characteristics were observed with age (44 years old, 26–58 for M-SCA vs. 57 years old, 31–68 for MCA, p=0.011) and location within the pancreas (64% in head for M-SCA vs. 85% in body or tail for MCA, p=0.013). No significant differences on EUS were observed between both groups regarding the type of loculation, cyst wall, and echo-pattern of cyst contents. But, many cases of M-SCA had microcysts (82%) when compared with 15% of MCA (p<0.001), and lobulated configuration of cyst was more frequently seen in M-SCA than MCA (91% vs. 25%, p=0.001). The combination of microcysts and lobulated configuration of cyst had sensitivity of 90%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 95% for the diagnosis of M-SCA when compared with MCA. Conclusions: M-SCA tends to occur at a relatively younger age than MCA and locate mainly in the head of the pancreas. While conventional imaging modalities display considerable morphologic overlap between M-SCA and MCA, EUS reveals characteristic findings including microcysts and lobulated configuration of cyst, which may help differentiate M-SCA from MCA.