Can EUS Help to Differentiate Macrocystic Serous Cystic Tumor From Mucinous Cystic Tumor of the Pancreas by its Morphologic Characteristics?

Abstract

Background: Benign pancreatic serous cystic tumor is usually morphologically distinguishable from mucinous cystic tumor (MCT), which require resection because of its malignant potential. A macrocystic variant of serous cystic tumor (M-SCT) recently has been described, making this important distinction more difficult. The aim of this study was to determine the EUS morphologic characteristics of M-SCT that can help differentiation from MCT. Methods: Clinical and EUS morphologic characteristics were studied in 27 consecutive patients with M-SCT and MCT who underwent surgery in Asan Medical Center from January 2001 to August 2004. EUS morphology was focused on several parameters including presence of microcysts (millimetric cysts around major cyst), configuration of cyst, septum-forming cyst (cyst or cyst-like lesion formed by internal septation within cyst). Results: Resection specimens were available for 10 M-SCTs and 17 MCTs. Significant differences were observed with regard to age (44.9 for M-SCT vs. 54.8 for MCT, p = 0.03) and location within the pancreas (80% in head for M-SCT vs. 82% in body or tail for MCT, p = 0.03). There were no significant differences of EUS morphologic characteristics between both groups regarding the type of loculation, presence of mural nodule and cyst wall, and echo-pattern of cyst contents. But, most of M-SCT had microcysts (80%) when compared with 18% of MCT (p = 0.02), and lobulated configuration of cyst was more frequently seen in M-SCT than MCT (90% vs. 18%, p = 0.001). Septum forming cyst was observed in 90% of M-SCT while it was observed in 23% of MCT (p = 0.001). The combination of microcysts, lobulated configuration of cyst, and septum-forming cyst had sensitivity of 70%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 85% for the diagnosis of M-SCT compared with MCT. Conclusions: M-SCT tends to occur at relatively younger age than MCT and be located mainly in head of pancreas. Although considerable morphological overlaps occur between M-SCT and MCT on conventional imaging modalities, EUS morphologic characteristics including microcysts, lobulated configuration of cyst, and septum-forming cyst may help to differentiate M-SCT from MCT. Background: Benign pancreatic serous cystic tumor is usually morphologically distinguishable from mucinous cystic tumor (MCT), which require resection because of its malignant potential. A macrocystic variant of serous cystic tumor (M-SCT) recently has been described, making this important distinction more difficult. The aim of this study was to determine the EUS morphologic characteristics of M-SCT that can help differentiation from MCT. Methods: Clinical and EUS morphologic characteristics were studied in 27 consecutive patients with M-SCT and MCT who underwent surgery in Asan Medical Center from January 2001 to August 2004. EUS morphology was focused on several parameters including presence of microcysts (millimetric cysts around major cyst), configuration of cyst, septum-forming cyst (cyst or cyst-like lesion formed by internal septation within cyst). Results: Resection specimens were available for 10 M-SCTs and 17 MCTs. Significant differences were observed with regard to age (44.9 for M-SCT vs. 54.8 for MCT, p = 0.03) and location within the pancreas (80% in head for M-SCT vs. 82% in body or tail for MCT, p = 0.03). There were no significant differences of EUS morphologic characteristics between both groups regarding the type of loculation, presence of mural nodule and cyst wall, and echo-pattern of cyst contents. But, most of M-SCT had microcysts (80%) when compared with 18% of MCT (p = 0.02), and lobulated configuration of cyst was more frequently seen in M-SCT than MCT (90% vs. 18%, p = 0.001). Septum forming cyst was observed in 90% of M-SCT while it was observed in 23% of MCT (p = 0.001). The combination of microcysts, lobulated configuration of cyst, and septum-forming cyst had sensitivity of 70%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 85% for the diagnosis of M-SCT compared with MCT. Conclusions: M-SCT tends to occur at relatively younger age than MCT and be located mainly in head of pancreas. Although considerable morphological overlaps occur between M-SCT and MCT on conventional imaging modalities, EUS morphologic characteristics including microcysts, lobulated configuration of cyst, and septum-forming cyst may help to differentiate M-SCT from MCT.